Climate and average weather in Arlington
In Arlington, the summers are warm, fairly dry, and mostly clear and the winters are cold, snowy, and mostly cloudy.
Over the course of the year, the temperature in Arlington typically varies from 35°F to 73°F, and is rarely below 24°F or above 83°F. August is the hottest month of the year, while December is the coldest.
Based on the travel score, the best time of year to visit Arlington for warm-weather activities is from late June to mid September.
- Hottest
- Aug
- 73°
- Coldest
- Dec
- 35°
- Wettest
- Nov
- 10.4 in
- Driest
- Jul
- 1.3 in
- Rain / yr
- 68.4 in
- 165 wet days
- Daylight
- 8.1–15.9 h
- shortest–longest
- Elevation
- 115 ft
- 48.2°N
- Clearest
- Jul
- 43% cloud
Arlington is city in northern Snohomish County, Washington, United States.
- Density
- 790/km²
- people per km²
- Founded
- 1903
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Arlington weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around late June to mid September.
Temperature through the year
Daily average highs and lows in Arlington, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 3.0 months, from June 19 to September 18, with daily high temperatures above 66°F. The hottest month of the year in Arlington is August, with an average high of 73°F and low of 55°F.
The cool season lasts 3.7 months, from November 13 to March 5, with daily high temperatures below 49°F. The coldest month of the year in Arlington is December, with an average low of 35°F and high of 43°F.
Days typically run about 13°F warmer than nights, with the widest day–night swing (around 18°F) in August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 44 | 47 | 51 | 56 | 62 | 66 | 72 | 73 | 67 | 57 | 48 | 43 |
| Avg low (°F) | 36 | 36 | 38 | 42 | 47 | 51 | 55 | 55 | 50 | 44 | 38 | 35 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| Jan | 44 | 36 |
| Feb | 47 | 36 |
| Mar | 51 | 38 |
| Apr | 56 | 42 |
| May | 62 | 47 |
| Jun | 66 | 51 |
| Jul | 72 | 55 |
| Aug | 73 | 55 |
| Sep | 67 | 50 |
| Oct | 57 | 44 |
| Nov | 48 | 38 |
| Dec | 43 | 35 |
How hot and cold Arlington really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the coldest nights, wind chill pulls the feels-like down to about 29°F (around January 1), with roughly 101 freezing days a year (feels-like at or below 32°F), worst in January.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°F) | 44 | 47 | 51 | 56 | 62 | 66 | 72 | 73 | 67 | 57 | 48 | 43 |
| Air high (°F) | 44 | 47 | 51 | 56 | 62 | 66 | 72 | 73 | 67 | 57 | 48 | 43 |
| Feels-like low (°F) | 30 | 31 | 34 | 39 | 46 | 51 | 55 | 55 | 50 | 41 | 34 | 30 |
| Air low (°F) | 36 | 36 | 38 | 42 | 47 | 51 | 55 | 55 | 50 | 44 | 38 | 35 |
| Feels-like high (°F) | Air high (°F) | Feels-like low (°F) | Air low (°F) | |
|---|---|---|---|---|
| Jan | 44 | 44 | 30 | 36 |
| Feb | 47 | 47 | 31 | 36 |
| Mar | 51 | 51 | 34 | 38 |
| Apr | 56 | 56 | 39 | 42 |
| May | 62 | 62 | 46 | 47 |
| Jun | 66 | 66 | 51 | 51 |
| Jul | 72 | 72 | 55 | 55 |
| Aug | 73 | 73 | 55 | 55 |
| Sep | 67 | 67 | 50 | 50 |
| Oct | 57 | 57 | 41 | 44 |
| Nov | 48 | 48 | 34 | 38 |
| Dec | 43 | 43 | 30 | 35 |
Average hourly temperature in Arlington
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on August afternoons, near 73°F, and coldest before dawn in December, near 35°F.
Arlington weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 44° / 36° | 9.3 | 19.1 | 5.3 | 8.6 | 0.6 |
| Feb | 47° / 36° | 6.1 | 15.5 | 4.5 | 9.9 | 1.2 |
| Mar | 51° / 38° | 7.6 | 19.6 | 3.7 | 11.6 | 1.9 |
| Apr | 56° / 42° | 5.6 | 16.4 | 1 | 13.4 | 3.2 |
| May | 62° / 47° | 3.8 | 12.1 | 0.1 | 14.9 | 5.0 |
| Jun | 66° / 51° | 2.8 | 9.8 | 0 | 15.8 | 6.0 |
| Jul | 72° / 55° | 1.3 | 5.2 | 0 | 15.5 | 7.8 |
| Aug | 73° / 55° | 1.6 | 5.5 | 0 | 14.1 | 7.8 |
| Sep | 67° / 50° | 3.4 | 8.8 | 0 | 12.4 | 6.5 |
| Oct | 57° / 44° | 7.2 | 14.9 | 0 | 10.6 | 3.7 |
| Nov | 48° / 38° | 10.4 | 19.2 | 2.2 | 9 | 1.4 |
| Dec | 43° / 35° | 9.3 | 19.2 | 6.1 | 8.2 | 0.4 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Arlington gets about 68.4 in of precipitation a year. On a typical day the chance of rain is very wet, but that rises and falls sharply with the seasons.
The wetter season lasts 6.6 months, from around Oct 12 to May 1, peaking in November at about 66% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jul 29.
November is the wettest month by volume, with 10.4 in over about 19 wet days; July is the driest, with 1.3 in. Some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 61 | 57 | 62 | 54 | 39 | 33 | 17 | 17 | 30 | 48 | 63 | 63 |
| Rain days | 19 | 16 | 20 | 16 | 12 | 10 | 5 | 6 | 9 | 15 | 19 | 19 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 61 | 19 |
| Feb | 57 | 16 |
| Mar | 62 | 20 |
| Apr | 54 | 16 |
| May | 39 | 12 |
| Jun | 33 | 10 |
| Jul | 17 | 5 |
| Aug | 17 | 6 |
| Sep | 30 | 9 |
| Oct | 48 | 15 |
| Nov | 63 | 19 |
| Dec | 63 | 19 |
Monthly rainfall
Over a full year, Arlington collects about 68.4 in of rain across 165 wet days — roughly 5.7 in in an average month.
It doesn’t fall evenly. November is the wettest month with 10.4 in, while July is the driest at just 1.3 in. The three wettest months alone bring about 42% of the year’s total, and some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (in) | 9.3 | 6.1 | 7.6 | 5.6 | 3.8 | 2.8 | 1.3 | 1.6 | 3.4 | 7.2 | 10.4 | 9.3 |
| Rain days | 19 | 16 | 20 | 16 | 12 | 10 | 5 | 6 | 9 | 15 | 19 | 19 |
| Snow days | 5 | 5 | 4 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 6 |
| Rainfall (in) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 9.3 | 19 | 5 |
| Feb | 6.1 | 16 | 5 |
| Mar | 7.6 | 20 | 4 |
| Apr | 5.6 | 16 | 1 |
| May | 3.8 | 12 | 0 |
| Jun | 2.8 | 10 | 0 |
| Jul | 1.3 | 5 | 0 |
| Aug | 1.6 | 6 | 0 |
| Sep | 3.4 | 9 | 0 |
| Oct | 7.2 | 15 | 0 |
| Nov | 10.4 | 19 | 2 |
| Dec | 9.3 | 19 | 6 |
Snow in Arlington
Average snowy days through the year, the snow-season span, and estimated snowfall — for ski trips and the perennial 'will there be snow at Christmas?' question.
Arlington averages about 23 snowy days a year. Snow season runs roughly Nov 3 to Apr 21 — about 5.6 months.
December is snowiest, with roughly 6 days of snow and an estimated 12 in of snowfall. Over the year that adds up to an estimated 38 in of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 5 | 5 | 4 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 6 |
| Snowfall (in) | 9 | 8 | 6 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 12 |
| Snow days | Snowfall (in) | |
|---|---|---|
| Jan | 5 | 9 |
| Feb | 5 | 8 |
| Mar | 4 | 6 |
| Apr | 1 | 1 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 2 | 3 |
| Dec | 6 | 12 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Arlington, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around June 15 and lasts for 3.9 months, ending around October 10. The clearest month is August, when the sky is clear, mostly clear, or partly cloudy 65% of the time on average.
The cloudier part of the year begins around October 11 and lasts for 6.7 months, ending around May 3. The cloudiest month is December, when it is overcast or mostly cloudy 78% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 23 | 29 | 27 | 31 | 37 | 41 | 64 | 65 | 57 | 36 | 24 | 22 |
| Cloudier (%) | 77 | 71 | 73 | 69 | 63 | 59 | 36 | 35 | 43 | 64 | 76 | 78 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 23 | 77 |
| Feb | 29 | 71 |
| Mar | 27 | 73 |
| Apr | 31 | 69 |
| May | 37 | 63 |
| Jun | 41 | 59 |
| Jul | 64 | 36 |
| Aug | 65 | 35 |
| Sep | 57 | 43 |
| Oct | 36 | 64 |
| Nov | 24 | 76 |
| Dec | 22 | 78 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 18, brings about 15 h 54 min of light; the shortest, around December 18, only 8 h 06 min — a swing of roughly 7 h 48 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 8.6 | 9.9 | 11.6 | 13.4 | 14.9 | 15.8 | 15.5 | 14.1 | 12.4 | 10.6 | 9.0 | 8.2 |
| Sunrise (AM) | 8:01 | 7:26 | 6:31 | 5:26 | 4:36 | 4:14 | 4:29 | 5:09 | 5:52 | 6:37 | 7:25 | 8:00 |
| Sunset (PM) | 4:34 | 5:20 | 6:05 | 6:51 | 7:34 | 8:04 | 7:59 | 7:17 | 6:13 | 5:10 | 4:23 | 4:09 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 8.6 | 8:01 | 4:34 |
| Feb | 9.9 | 7:26 | 5:20 |
| Mar | 11.6 | 6:31 | 6:05 |
| Apr | 13.4 | 5:26 | 6:51 |
| May | 14.9 | 4:36 | 7:34 |
| Jun | 15.8 | 4:14 | 8:04 |
| Jul | 15.5 | 4:29 | 7:59 |
| Aug | 14.1 | 5:09 | 7:17 |
| Sep | 12.4 | 5:52 | 6:13 |
| Oct | 10.6 | 6:37 | 5:10 |
| Nov | 9.0 | 7:25 | 4:23 |
| Dec | 8.2 | 8:00 | 4:09 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Arlington averages about 8 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 3 and 17 days.
The sunnier stretch runs 3.7 months, from around Jun 21 to Oct 12. The sunniest month is July, with roughly 15 sunny days (mixed).
The greyest month is December, down near 4 sunny days — about 72% fewer than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 5 | 5 | 5 | 5 | 7 | 7 | 15 | 15 | 12 | 8 | 5 | 4 |
| Sky | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Mixed | Mixed | Mixed | Gloomy | Gloomy | Gloomy |
| Sunny days | Sky | |
|---|---|---|
| Jan | 5 | Gloomy |
| Feb | 5 | Gloomy |
| Mar | 5 | Gloomy |
| Apr | 5 | Gloomy |
| May | 7 | Gloomy |
| Jun | 7 | Gloomy |
| Jul | 15 | Mixed |
| Aug | 15 | Mixed |
| Sep | 12 | Mixed |
| Oct | 8 | Gloomy |
| Nov | 5 | Gloomy |
| Dec | 4 | Gloomy |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In Arlington, the air stays dry or comfortable essentially all year. Even in July, the muggiest month, it feels humid or worse only about 2% of the time — humidity is not something you need to plan around here.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 100 | 100 | 100 | 100 | 98 | 91 | 71 | 65 | 83 | 98 | 100 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 0 | 2 | 9 | 28 | 33 | 17 | 2 | 0 | 0 |
| Humid (%) | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 2 | 0 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | |
|---|---|---|---|
| Jan | 100 | 0 | 0 |
| Feb | 100 | 0 | 0 |
| Mar | 100 | 0 | 0 |
| Apr | 100 | 0 | 0 |
| May | 98 | 2 | 0 |
| Jun | 91 | 9 | 0 |
| Jul | 71 | 28 | 2 |
| Aug | 65 | 33 | 2 |
| Sep | 83 | 17 | 0 |
| Oct | 98 | 2 | 0 |
| Nov | 100 | 0 | 0 |
| Dec | 100 | 0 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Arlington is typically calm, near 5 mph, and varies little with the seasons.
The windier part of the year lasts 6.2 months, from around Oct 14 to Apr 19. The windiest month is December, averaging about 6 mph (calm).
The calmer part of the year runs from around Apr 20 to Oct 13, with August the calmest month at about 4 mph.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 6 | 6 | 5 | 5 | 4 | 4 | 4 | 4 | 4 | 5 | 6 | 6 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (mph) | Feels | |
|---|---|---|
| Jan | 6 | calm |
| Feb | 6 | calm |
| Mar | 5 | calm |
| Apr | 5 | calm |
| May | 4 | calm |
| Jun | 4 | calm |
| Jul | 4 | calm |
| Aug | 4 | calm |
| Sep | 4 | calm |
| Oct | 5 | calm |
| Nov | 6 | calm |
| Dec | 6 | calm |
Hazard calendar for Arlington
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Arlington's rainy season runs October–April, when most of the year's rain falls.
Best time to visit Arlington
To characterize how pleasant the weather is in Arlington throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around late August, Arlington is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 64°F and 82°F. Based on this score, the best time of year to visit Arlington for general outdoor tourist activities is from late June to mid September, with a peak score in the last week of July.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 0.6 | 1.2 | 1.9 | 3.2 | 5.0 | 6.1 | 7.7 | 7.8 | 6.4 | 3.7 | 1.4 | 0.4 |
| Rating | poor | poor | poor | poor | fair | good | ideal | ideal | good | fair | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 0.6 | poor |
| Feb | 1.2 | poor |
| Mar | 1.9 | poor |
| Apr | 3.2 | poor |
| May | 5.0 | fair |
| Jun | 6.1 | good |
| Jul | 7.7 | ideal |
| Aug | 7.8 | ideal |
| Sep | 6.4 | good |
| Oct | 3.7 | fair |
| Nov | 1.4 | poor |
| Dec | 0.4 | poor |
The beach/pool score favors clear, rainless days with daytime highs between 75°F and 93°F. Based on this score, the best time of year to visit Arlington for hot-weather activities is from mid July to late August, with a peak score in the last week of July.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Arlington, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around August (highs near 73°F), the essentials are light clothes and sun protection. In the cold season around December (highs near 43°F), pack a warm layer, a heavy coat and rain gear.
In August, Arlington sees daytime highs around 73°F and nights near 55°F. Worth packing: light clothes and sun protection. About 6 days see rain.
Sea temperature near Arlington
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea at the nearest coast (about 35 mi away) is warmest in August at about 53°F and coldest in February near 46°F.
The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 46 | 46 | 47 | 48 | 50 | 52 | 53 | 53 | 53 | 50 | 49 | 47 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 46 | Bracing |
| Feb | 46 | Bracing |
| Mar | 47 | Bracing |
| Apr | 48 | Bracing |
| May | 50 | Bracing |
| Jun | 52 | Bracing |
| Jul | 53 | Bracing |
| Aug | 53 | Bracing |
| Sep | 53 | Bracing |
| Oct | 50 | Bracing |
| Nov | 49 | Bracing |
| Dec | 47 | Bracing |
UV index (midday) in Arlington by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in Arlington peaks around July 17 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 18 at about 1 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 1 | 1 | 4 | 5 | 7 | 6 | 8 | 6 | 4 | 3 | 1 | 1 |
| Level | Low | Low | Moderate | Moderate | High | High | Very high | High | Moderate | Moderate | Low | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 1 | Low |
| Feb | 1 | Low |
| Mar | 4 | Moderate |
| Apr | 5 | Moderate |
| May | 7 | High |
| Jun | 6 | High |
| Jul | 8 | Very high |
| Aug | 6 | High |
| Sep | 4 | Moderate |
| Oct | 3 | Moderate |
| Nov | 1 | Low |
| Dec | 1 | Low |
Average hourly UV index in Arlington
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in July the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 0 | 0 | 3 | 5 | 7.5 | 7 | 8.5 | 7 | 4 | 0 | 0 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 0 | 3 | 0.5 | 5 | 1.5 | 0 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 0 | 0 |
| Mar | 3 | 0 |
| Apr | 5 | 0 |
| May | 7.5 | 3 |
| Jun | 7 | 0.5 |
| Jul | 8.5 | 5 |
| Aug | 7 | 1.5 |
| Sep | 4 | 0 |
| Oct | 0 | 0 |
| Nov | 0 | 0 |
| Dec | 0 | 0 |
Air quality in Arlington by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in Arlington is worst in August — around 20 µg/m³ PM2.5 (moderate), about 3.1× the cleanest month (December, 6 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 8 | 10 | 12 | 12 | 13 | 11 | 10 | 20 | 18 | 11 | 7 | 6 |
| Level | Good | Good | Moderate | Good | Moderate | Good | Good | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 8 | Good |
| Feb | 10 | Good |
| Mar | 12 | Moderate |
| Apr | 12 | Good |
| May | 13 | Moderate |
| Jun | 11 | Good |
| Jul | 10 | Good |
| Aug | 20 | Moderate |
| Sep | 18 | Moderate |
| Oct | 11 | Good |
| Nov | 7 | Good |
| Dec | 6 | Good |
Growing season
Arlington is mild enough that a frost-free day stays more likely than not even in midwinter. Nights are reliably above freezing from about March 17 to November 3 (232 days); outside that window a hard frost is an occasional risk.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 70 | 75 | 88 | 98 | 100 | 100 | 100 | 100 | 100 | 97 | 83 | 68 |
| Frost nights | 31 | 28 | 14 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 30 | 31 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 70 | 31 |
| Feb | 75 | 28 |
| Mar | 88 | 14 |
| Apr | 98 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 97 | 0 |
| Nov | 83 | 30 |
| Dec | 68 | 31 |
Growing degree days
Growing degree days tally heat above 50°F: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Arlington banks about 1,559 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°F·days) | 0 | 0 | 0 | 8 | 145 | 259 | 416 | 427 | 263 | 41 | 0 | 0 |
| Growing degree days (°F·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 0 |
| Apr | 8 |
| May | 145 |
| Jun | 259 |
| Jul | 416 |
| Aug | 427 |
| Sep | 263 |
| Oct | 41 |
| Nov | 0 |
| Dec | 0 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Arlington receives about 3.4 kWh/m² a day of solar energy on average — moderate — with a clear seasonal swing between 0.8 and 6.2 kWh/m².
The brighter stretch of the year lasts 6.0 months, from around Mar 28 to Sep 25. The brightest month is July, averaging about 6.1 kWh/m² (intense).
The dimmest month is December, down near 0.8 kWh/m² — roughly 86% less than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 1.0 | 1.9 | 2.9 | 4.3 | 5.3 | 5.6 | 6.2 | 5.4 | 4.0 | 2.2 | 1.1 | 0.8 |
| Level | Dim | Dim | Moderate | Bright | Bright | Bright | Intense | Bright | Bright | Moderate | Dim | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 1.0 | Dim |
| Feb | 1.9 | Dim |
| Mar | 2.9 | Moderate |
| Apr | 4.3 | Bright |
| May | 5.3 | Bright |
| Jun | 5.6 | Bright |
| Jul | 6.2 | Intense |
| Aug | 5.4 | Bright |
| Sep | 4.0 | Bright |
| Oct | 2.2 | Moderate |
| Nov | 1.1 | Dim |
| Dec | 0.8 | Dim |
Where is Arlington?
Arlington sits at 48.2°N, 122.1°W, 115 ft above sea level, in United States. The nearest listed city is Marysville, 11 mi away.
Topography around Arlington
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Arlington.
Within 2 miles, the terrain around Arlington has only modest variations in elevation — a maximum elevation change of 479 ft around an average of 157 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,297 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 10,755 ft.
The land around Arlington is covered by trees (51%) and grassland (32%) within 2 miles, trees (76%) within 10 miles, and trees (66%) and water (21%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Arlington (48.1987°, -122.1251°, elevation 115 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).