Climate and average weather in Arcata
In Arcata, the summers are mild, dry, and clear and the winters are cool, snowy, and partly cloudy.
Over the course of the year, the temperature in Arcata typically varies from 40°F to 67°F, and is rarely below 35°F or above 74°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 Arcata for warm-weather activities is from late June to early October.
- Hottest
- Aug
- 67°
- Coldest
- Dec
- 40°
- Wettest
- Dec
- 10.1 in
- Driest
- Jul
- 0.1 in
- Rain / yr
- 51.3 in
- 104 wet days
- Daylight
- 9.1–14.9 h
- shortest–longest
- Elevation
- 23 ft
- 40.9°N
- Clearest
- Jul
- 27% cloud
Arcata is city in Humboldt County, California, United States.
- Density
- 627/km²
- people per km²
- Founded
- 1858
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Arcata 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 early October.
Temperature through the year
Daily average highs and lows in Arcata, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 3.5 months, from June 24 to October 7, with daily high temperatures above 63°F. The hottest month of the year in Arcata is August, with an average high of 67°F and low of 53°F.
The cool season lasts 4.5 months, from November 21 to April 5, with daily high temperatures below 53°F. The coldest month of the year in Arcata is December, with an average low of 40°F and high of 50°F.
Days typically run about 12°F warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 51 | 52 | 53 | 55 | 58 | 62 | 66 | 67 | 66 | 61 | 55 | 50 |
| Avg low (°F) | 41 | 41 | 42 | 44 | 47 | 50 | 53 | 53 | 52 | 48 | 44 | 40 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| Jan | 51 | 41 |
| Feb | 52 | 41 |
| Mar | 53 | 42 |
| Apr | 55 | 44 |
| May | 58 | 47 |
| Jun | 62 | 50 |
| Jul | 66 | 53 |
| Aug | 67 | 53 |
| Sep | 66 | 52 |
| Oct | 61 | 48 |
| Nov | 55 | 44 |
| Dec | 50 | 40 |
Average hourly temperature in Arcata
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 67°F, and coldest before dawn in December, near 40°F.
Arcata 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 | 51° / 41° | 8.6 | 15.4 | 1.8 | 9.4 | 2.2 |
| Feb | 52° / 41° | 7.1 | 13.1 | 2.4 | 10.4 | 2.4 |
| Mar | 53° / 42° | 7.4 | 14.7 | 2.7 | 11.7 | 2.6 |
| Apr | 55° / 44° | 4.4 | 11.8 | 1 | 13.1 | 3.3 |
| May | 58° / 47° | 2.4 | 7.2 | 0.1 | 14.2 | 4.7 |
| Jun | 62° / 50° | 1.0 | 3.8 | 0 | 14.9 | 6.3 |
| Jul | 66° / 53° | 0.1 | 0.8 | 0 | 14.6 | 8.0 |
| Aug | 67° / 53° | 0.2 | 0.9 | 0 | 13.6 | 8.1 |
| Sep | 66° / 52° | 0.7 | 2.5 | 0 | 12.3 | 7.7 |
| Oct | 61° / 48° | 3.2 | 6.4 | 0 | 10.9 | 5.9 |
| Nov | 55° / 44° | 6.2 | 12.3 | 0.5 | 9.7 | 3.2 |
| Dec | 50° / 40° | 10.1 | 15.4 | 1.7 | 9.1 | 2.1 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Arcata gets about 51.3 in of precipitation a year. On a typical day the chance of rain is some rain, but that rises and falls sharply with the seasons.
The wetter season lasts 5.9 months, from around Nov 1 to Apr 28, peaking in December at about 51% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jul 27.
December is the wettest month by volume, with 10.1 in over about 15 wet days; July is the driest, with 0.1 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 (%) | 49 | 47 | 47 | 40 | 24 | 12 | 3 | 3 | 9 | 20 | 41 | 49 |
| Rain days | 15 | 13 | 15 | 12 | 7 | 4 | 1 | 1 | 3 | 6 | 12 | 15 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 49 | 15 |
| Feb | 47 | 13 |
| Mar | 47 | 15 |
| Apr | 40 | 12 |
| May | 24 | 7 |
| Jun | 12 | 4 |
| Jul | 3 | 1 |
| Aug | 3 | 1 |
| Sep | 9 | 3 |
| Oct | 20 | 6 |
| Nov | 41 | 12 |
| Dec | 49 | 15 |
Monthly rainfall
Over a full year, Arcata collects about 51.3 in of rain across 104 wet days — roughly 4.3 in in an average month.
It doesn’t fall evenly. December is the wettest month with 10.1 in, while July is the driest at just 0.1 in. The three wettest months alone bring about 51% 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) | 8.6 | 7.1 | 7.4 | 4.4 | 2.4 | 1.0 | 0.1 | 0.2 | 0.7 | 3.2 | 6.2 | 10.1 |
| Rain days | 15 | 13 | 15 | 12 | 7 | 4 | 1 | 1 | 3 | 6 | 12 | 15 |
| Snow days | 2 | 2 | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
| Rainfall (in) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 8.6 | 15 | 2 |
| Feb | 7.1 | 13 | 2 |
| Mar | 7.4 | 15 | 3 |
| Apr | 4.4 | 12 | 1 |
| May | 2.4 | 7 | 0 |
| Jun | 1.0 | 4 | 0 |
| Jul | 0.1 | 1 | 0 |
| Aug | 0.2 | 1 | 0 |
| Sep | 0.7 | 3 | 0 |
| Oct | 3.2 | 6 | 0 |
| Nov | 6.2 | 12 | 1 |
| Dec | 10.1 | 15 | 2 |
Snow in Arcata
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.
Arcata averages about 10 snowy days a year. Snow season runs roughly Nov 18 to Apr 21 — about 5.1 months.
February is snowiest, with roughly 3 days of snow and an estimated 6 in of snowfall. Over the year that adds up to an estimated 17 in of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 2 | 2 | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
| Snowfall (in) | 2 | 6 | 4 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
| Snow days | Snowfall (in) | |
|---|---|---|
| Jan | 2 | 2 |
| Feb | 2 | 6 |
| Mar | 3 | 4 |
| Apr | 1 | 1 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 1 | 1 |
| Dec | 2 | 3 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Arcata, 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 May 27 and lasts for 5.2 months, ending around October 30. The clearest month is August, when the sky is clear, mostly clear, or partly cloudy 89% of the time on average.
The cloudier part of the year begins around October 31 and lasts for 6.8 months, ending around May 26. The cloudiest month is January, when it is overcast or mostly cloudy 67% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 33 | 34 | 37 | 43 | 55 | 72 | 88 | 89 | 83 | 68 | 43 | 34 |
| Cloudier (%) | 67 | 66 | 63 | 57 | 45 | 28 | 12 | 11 | 17 | 32 | 57 | 66 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 33 | 67 |
| Feb | 34 | 66 |
| Mar | 37 | 63 |
| Apr | 43 | 57 |
| May | 55 | 45 |
| Jun | 72 | 28 |
| Jul | 88 | 12 |
| Aug | 89 | 11 |
| Sep | 83 | 17 |
| Oct | 68 | 32 |
| Nov | 43 | 57 |
| Dec | 34 | 66 |
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 10, brings about 14 h 54 min of light; the shortest, around January 1, only 9 h 06 min — a swing of roughly 5 h 48 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 9.4 | 10.4 | 11.7 | 13.1 | 14.2 | 14.9 | 14.6 | 13.6 | 12.3 | 10.9 | 9.7 | 9.1 |
| Sunrise (AM) | 7:44 | 7:20 | 6:36 | 5:44 | 5:04 | 4:49 | 5:02 | 5:31 | 6:03 | 6:35 | 7:11 | 7:40 |
| Sunset (PM) | 5:07 | 5:42 | 6:16 | 6:49 | 7:21 | 7:44 | 7:42 | 7:10 | 6:19 | 5:28 | 4:52 | 4:45 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 9.4 | 7:44 | 5:07 |
| Feb | 10.4 | 7:20 | 5:42 |
| Mar | 11.7 | 6:36 | 6:16 |
| Apr | 13.1 | 5:44 | 6:49 |
| May | 14.2 | 5:04 | 7:21 |
| Jun | 14.9 | 4:49 | 7:44 |
| Jul | 14.6 | 5:02 | 7:42 |
| Aug | 13.6 | 5:31 | 7:10 |
| Sep | 12.3 | 6:03 | 6:19 |
| Oct | 10.9 | 6:35 | 5:28 |
| Nov | 9.7 | 7:11 | 4:52 |
| Dec | 9.1 | 7:40 | 4:45 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Arcata averages about 13 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 6 and 22 days.
The sunnier stretch runs 4.9 months, from around Jun 5 to Oct 31. The sunniest month is August, with roughly 22 sunny days (bright).
The greyest month is January, down near 7 sunny days — about 68% fewer than the August peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 7 | 7 | 8 | 8 | 11 | 16 | 22 | 22 | 20 | 17 | 9 | 7 |
| Sky | Gloomy | Gloomy | Gloomy | Mixed | Mixed | Bright | Bright | Bright | Bright | Bright | Mixed | Gloomy |
| Sunny days | Sky | |
|---|---|---|
| Jan | 7 | Gloomy |
| Feb | 7 | Gloomy |
| Mar | 8 | Gloomy |
| Apr | 8 | Mixed |
| May | 11 | Mixed |
| Jun | 16 | Bright |
| Jul | 22 | Bright |
| Aug | 22 | Bright |
| Sep | 20 | Bright |
| Oct | 17 | Bright |
| Nov | 9 | Mixed |
| Dec | 7 | 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 Arcata, the air stays dry or comfortable essentially all year. Even in July, the muggiest month, it feels humid or worse only about 0% 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 | 99 | 95 | 85 | 84 | 92 | 98 | 100 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 0 | 1 | 5 | 15 | 16 | 8 | 2 | 0 | 0 |
| Dry (%) | Comfortable (%) | |
|---|---|---|
| Jan | 100 | 0 |
| Feb | 100 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 99 | 1 |
| Jun | 95 | 5 |
| Jul | 85 | 15 |
| Aug | 84 | 16 |
| Sep | 92 | 8 |
| Oct | 98 | 2 |
| Nov | 100 | 0 |
| Dec | 100 | 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 Arcata is typically calm, near 6 mph, and varies little with the seasons.
The windier part of the year lasts 7.4 months, from around Nov 18 to Jun 30. The windiest month is December, averaging about 7 mph (calm).
The calmer part of the year runs from around Jul 1 to Nov 17, with September the calmest month at about 5 mph.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 7 | 7 | 7 | 7 | 7 | 7 | 6 | 5 | 5 | 5 | 6 | 7 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (mph) | Feels | |
|---|---|---|
| Jan | 7 | calm |
| Feb | 7 | calm |
| Mar | 7 | calm |
| Apr | 7 | calm |
| May | 7 | calm |
| Jun | 7 | calm |
| Jul | 6 | calm |
| Aug | 5 | calm |
| Sep | 5 | calm |
| Oct | 5 | calm |
| Nov | 6 | calm |
| Dec | 7 | calm |
Hazard calendar for Arcata
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Arcata's rainy season runs November–March, when most of the year's rain falls.
Best time to visit Arcata
To characterize how pleasant the weather is in Arcata throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around late September, Arcata 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 Arcata for general outdoor tourist activities is from late June to early October, 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) | 2.2 | 2.4 | 2.6 | 3.3 | 4.7 | 6.4 | 8.0 | 8.1 | 7.7 | 5.9 | 3.3 | 2.1 |
| Rating | poor | poor | poor | poor | fair | good | ideal | ideal | ideal | good | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 2.2 | poor |
| Feb | 2.4 | poor |
| Mar | 2.6 | poor |
| Apr | 3.3 | poor |
| May | 4.7 | fair |
| Jun | 6.4 | good |
| Jul | 8.0 | ideal |
| Aug | 8.1 | ideal |
| Sep | 7.7 | ideal |
| Oct | 5.9 | good |
| Nov | 3.3 | poor |
| Dec | 2.1 | 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 Arcata for hot-weather activities is from mid July to mid September, 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 Arcata, 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 67°F), the essentials are sun protection. In the cold season around December (highs near 50°F), pack a warm layer and rain gear.
In August, Arcata sees daytime highs around 67°F and nights near 53°F. Pack sun protection.
Sea temperature near Arcata
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea offshore is warmest in August at about 55°F and coldest in March near 51°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) | 52 | 52 | 51 | 52 | 52 | 53 | 54 | 55 | 55 | 54 | 53 | 53 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 52 | Bracing |
| Feb | 52 | Bracing |
| Mar | 51 | Bracing |
| Apr | 52 | Bracing |
| May | 52 | Bracing |
| Jun | 53 | Bracing |
| Jul | 54 | Bracing |
| Aug | 55 | Bracing |
| Sep | 55 | Bracing |
| Oct | 54 | Bracing |
| Nov | 53 | Bracing |
| Dec | 53 | Bracing |
UV index (midday) in Arcata 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 Arcata peaks around June 21 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 15 at about 2 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 3 | 5 | 6 | 9 | 10 | 9 | 8 | 5 | 5 | 2 | 2 |
| Level | Low | Moderate | Moderate | High | Very high | Very high | Very high | Very high | High | Moderate | Low | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Low |
| Feb | 3 | Moderate |
| Mar | 5 | Moderate |
| Apr | 6 | High |
| May | 9 | Very high |
| Jun | 10 | Very high |
| Jul | 9 | Very high |
| Aug | 8 | Very high |
| Sep | 5 | High |
| Oct | 5 | Moderate |
| Nov | 2 | Low |
| Dec | 2 | Low |
Average hourly UV index in Arcata
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 June the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 6 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 | 5 | 6.5 | 8 | 8.5 | 8.5 | 7.5 | 5.5 | 4.5 | 0 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 1 | 5 | 6 | 5.5 | 4.5 | 0 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 0 | 0 |
| Mar | 5 | 0 |
| Apr | 6.5 | 1 |
| May | 8 | 5 |
| Jun | 8.5 | 6 |
| Jul | 8.5 | 5.5 |
| Aug | 7.5 | 4.5 |
| Sep | 5.5 | 0 |
| Oct | 4.5 | 0 |
| Nov | 0 | 0 |
| Dec | 0 | 0 |
Air quality in Arcata 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 Arcata is worst in September — around 116 µg/m³ PM2.5 (unhealthy), about 23.7× the cleanest month (January, 5 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) | 5 | 7 | 7 | 7 | 6 | 6 | 12 | 85 | 116 | 16 | 6 | 5 |
| Level | Good | Good | Good | Good | Good | Good | Good | Unhealthy | Unhealthy | Moderate | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 5 | Good |
| Feb | 7 | Good |
| Mar | 7 | Good |
| Apr | 7 | Good |
| May | 6 | Good |
| Jun | 6 | Good |
| Jul | 12 | Good |
| Aug | 85 | Unhealthy |
| Sep | 116 | Unhealthy |
| Oct | 16 | Moderate |
| Nov | 6 | Good |
| Dec | 5 | Good |
Growing season
Arcata is frost-free year round — even the coldest nights rarely reach freezing, so there is no start or end to the growing season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 97 | 98 | 99 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 99 | 97 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 97 | 0 |
| Feb | 98 | 0 |
| Mar | 99 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 99 | 0 |
| Dec | 97 | 0 |
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. Arcata banks about 1,292 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 | 3 | 75 | 172 | 298 | 323 | 269 | 144 | 8 | 0 |
| Growing degree days (°F·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 0 |
| Apr | 3 |
| May | 75 |
| Jun | 172 |
| Jul | 298 |
| Aug | 323 |
| Sep | 269 |
| Oct | 144 |
| Nov | 8 |
| 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.
Arcata receives about 4.7 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 1.6 and 7.9 kWh/m².
The brighter stretch of the year lasts 6.0 months, from around Mar 31 to Sep 30. The brightest month is July, averaging about 7.7 kWh/m² (intense).
The dimmest month is December, down near 1.7 kWh/m² — roughly 79% less than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 1.9 | 2.7 | 4.0 | 5.4 | 6.7 | 7.5 | 7.8 | 6.9 | 5.6 | 3.8 | 2.2 | 1.6 |
| Level | Dim | Moderate | Moderate | Bright | Intense | Intense | Intense | Intense | Bright | Moderate | Moderate | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 1.9 | Dim |
| Feb | 2.7 | Moderate |
| Mar | 4.0 | Moderate |
| Apr | 5.4 | Bright |
| May | 6.7 | Intense |
| Jun | 7.5 | Intense |
| Jul | 7.8 | Intense |
| Aug | 6.9 | Intense |
| Sep | 5.6 | Bright |
| Oct | 3.8 | Moderate |
| Nov | 2.2 | Moderate |
| Dec | 1.6 | Dim |
Where is Arcata?
Arcata sits at 40.9°N, 124.1°W, 23 ft above sea level, in United States. The nearest listed city is Bayside, 1.9 mi away.
Topography around Arcata
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Arcata.
Within 2 miles, the terrain around Arcata has significant variations in elevation — a maximum elevation change of 1,191 ft around an average of 157 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,690 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 7,415 ft.
The land around Arcata is covered by trees (40%) and grassland (29%) within 2 miles, trees (55%) and water (29%) within 10 miles, and trees (67%) and water (27%) 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 Arcata (40.8665°, -124.0828°, elevation 23 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).