Climate and average weather in West Lake Sammamish
In West Lake Sammamish, 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 West Lake Sammamish typically varies from 35°F to 74°F, and is rarely below 25°F or above 85°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 West Lake Sammamish for warm-weather activities is from late June to mid September.
- Hottest
- Aug
- 74°
- Coldest
- Dec
- 35°
- Wettest
- Nov
- 9.0 in
- Driest
- Jul
- 1.3 in
- Rain / yr
- 63.1 in
- 167 wet days
- Daylight
- 8.2–15.8 h
- shortest–longest
- Elevation
- 30 ft
- 47.6°N
- Clearest
- Aug
- 45% cloud
West Lake Sammamish is census designated place.
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
West Lake Sammamish 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 West Lake Sammamish, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 2.9 months, from June 21 to September 17, with daily high temperatures above 68°F. The hottest month of the year in West Lake Sammamish is August, with an average high of 74°F and low of 54°F.
The cool season lasts 3.6 months, from November 14 to March 3, with daily high temperatures below 50°F. The coldest month of the year in West Lake Sammamish is December, with an average low of 35°F and high of 44°F.
Days typically run about 15°F warmer than nights, with the widest day–night swing (around 20°F) in August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 45 | 48 | 52 | 57 | 63 | 67 | 74 | 74 | 68 | 58 | 49 | 44 |
| Avg low (°F) | 35 | 36 | 37 | 41 | 46 | 50 | 54 | 54 | 49 | 43 | 38 | 35 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| Jan | 45 | 35 |
| Feb | 48 | 36 |
| Mar | 52 | 37 |
| Apr | 57 | 41 |
| May | 63 | 46 |
| Jun | 67 | 50 |
| Jul | 74 | 54 |
| Aug | 74 | 54 |
| Sep | 68 | 49 |
| Oct | 58 | 43 |
| Nov | 49 | 38 |
| Dec | 44 | 35 |
How hot and cold West Lake Sammamish 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 106 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) | 45 | 48 | 52 | 57 | 63 | 67 | 74 | 74 | 68 | 58 | 49 | 44 |
| Air high (°F) | 45 | 48 | 52 | 57 | 63 | 67 | 74 | 74 | 68 | 58 | 49 | 44 |
| Feels-like low (°F) | 30 | 31 | 33 | 37 | 44 | 50 | 54 | 54 | 49 | 40 | 33 | 29 |
| Air low (°F) | 35 | 36 | 37 | 41 | 46 | 50 | 54 | 54 | 49 | 43 | 38 | 35 |
| Feels-like high (°F) | Air high (°F) | Feels-like low (°F) | Air low (°F) | |
|---|---|---|---|---|
| Jan | 45 | 45 | 30 | 35 |
| Feb | 48 | 48 | 31 | 36 |
| Mar | 52 | 52 | 33 | 37 |
| Apr | 57 | 57 | 37 | 41 |
| May | 63 | 63 | 44 | 46 |
| Jun | 67 | 67 | 50 | 50 |
| Jul | 74 | 74 | 54 | 54 |
| Aug | 74 | 74 | 54 | 54 |
| Sep | 68 | 68 | 49 | 49 |
| Oct | 58 | 58 | 40 | 43 |
| Nov | 49 | 49 | 33 | 38 |
| Dec | 44 | 44 | 29 | 35 |
Average hourly temperature in West Lake Sammamish
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 74°F, and coldest before dawn in December, near 35°F.
West Lake Sammamish 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 | 45° / 35° | 8.3 | 18.7 | 3.6 | 8.7 | 0.8 |
| Feb | 48° / 36° | 5.8 | 15.5 | 2.6 | 9.9 | 1.5 |
| Mar | 52° / 37° | 6.5 | 18.7 | 1.8 | 11.6 | 2.2 |
| Apr | 57° / 41° | 5.4 | 16.5 | 0.2 | 13.3 | 3.4 |
| May | 63° / 46° | 3.8 | 12.8 | 0 | 14.9 | 5.1 |
| Jun | 67° / 50° | 3.2 | 11.4 | 0 | 15.7 | 5.9 |
| Jul | 74° / 54° | 1.3 | 6.5 | 0 | 15.4 | 7.7 |
| Aug | 74° / 54° | 1.6 | 5.7 | 0 | 14.1 | 7.9 |
| Sep | 68° / 49° | 3.4 | 9 | 0 | 12.4 | 6.6 |
| Oct | 58° / 43° | 6.6 | 15.1 | 0 | 10.6 | 3.9 |
| Nov | 49° / 38° | 9.0 | 18.7 | 1 | 9.1 | 1.6 |
| Dec | 44° / 35° | 8.1 | 18.4 | 3.4 | 8.3 | 0.6 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
West Lake Sammamish gets about 63.1 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 6.8 months, from around Oct 11 to May 5, peaking in November at about 64% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Aug 1.
November is the wettest month by volume, with 9.0 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 (%) | 59 | 57 | 60 | 54 | 42 | 37 | 21 | 18 | 31 | 48 | 61 | 61 |
| Rain days | 19 | 16 | 19 | 17 | 13 | 11 | 7 | 6 | 9 | 15 | 19 | 18 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 59 | 19 |
| Feb | 57 | 16 |
| Mar | 60 | 19 |
| Apr | 54 | 17 |
| May | 42 | 13 |
| Jun | 37 | 11 |
| Jul | 21 | 7 |
| Aug | 18 | 6 |
| Sep | 31 | 9 |
| Oct | 48 | 15 |
| Nov | 61 | 19 |
| Dec | 61 | 18 |
Monthly rainfall
Over a full year, West Lake Sammamish collects about 63.1 in of rain across 167 wet days — roughly 5.3 in in an average month.
It doesn’t fall evenly. November is the wettest month with 9.0 in, while July is the driest at just 1.3 in. The three wettest months alone bring about 40% 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) | 8.3 | 5.8 | 6.5 | 5.4 | 3.8 | 3.2 | 1.3 | 1.6 | 3.4 | 6.6 | 9.0 | 8.1 |
| Rain days | 19 | 16 | 19 | 17 | 13 | 11 | 7 | 6 | 9 | 15 | 19 | 18 |
| Snow days | 4 | 3 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
| Rainfall (in) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 8.3 | 19 | 4 |
| Feb | 5.8 | 16 | 3 |
| Mar | 6.5 | 19 | 2 |
| Apr | 5.4 | 17 | 0 |
| May | 3.8 | 13 | 0 |
| Jun | 3.2 | 11 | 0 |
| Jul | 1.3 | 7 | 0 |
| Aug | 1.6 | 6 | 0 |
| Sep | 3.4 | 9 | 0 |
| Oct | 6.6 | 15 | 0 |
| Nov | 9.0 | 19 | 1 |
| Dec | 8.1 | 18 | 3 |
Snow in West Lake Sammamish
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.
West Lake Sammamish averages about 13 snowy days a year. Snow season runs roughly Nov 12 to Apr 8 — about 4.9 months.
December is snowiest, with roughly 3 days of snow and an estimated 6 in of snowfall. Over the year that adds up to an estimated 22 in of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 4 | 3 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
| Snowfall (in) | 6 | 5 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 6 |
| Snow days | Snowfall (in) | |
|---|---|---|
| Jan | 4 | 6 |
| Feb | 3 | 5 |
| Mar | 2 | 2 |
| Apr | 0 | 0 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 1 | 2 |
| Dec | 3 | 6 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In West Lake Sammamish, 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 19 and lasts for 3.8 months, ending around October 13. The clearest month is August, when the sky is clear, mostly clear, or partly cloudy 61% of the time on average.
The cloudier part of the year begins around October 14 and lasts for 8.1 months, ending around June 18. The cloudiest month is December, when it is overcast or mostly cloudy 79% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 24 | 28 | 26 | 27 | 32 | 36 | 59 | 61 | 55 | 37 | 25 | 21 |
| Cloudier (%) | 76 | 72 | 74 | 73 | 68 | 64 | 41 | 39 | 45 | 63 | 75 | 79 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 24 | 76 |
| Feb | 28 | 72 |
| Mar | 26 | 74 |
| Apr | 27 | 73 |
| May | 32 | 68 |
| Jun | 36 | 64 |
| Jul | 59 | 41 |
| Aug | 61 | 39 |
| Sep | 55 | 45 |
| Oct | 37 | 63 |
| Nov | 25 | 75 |
| Dec | 21 | 79 |
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 17, brings about 15 h 48 min of light; the shortest, around December 16, only 8 h 12 min — a swing of roughly 7 h 36 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 8.7 | 9.9 | 11.6 | 13.3 | 14.9 | 15.7 | 15.4 | 14.1 | 12.4 | 10.6 | 9.1 | 8.3 |
| Sunrise (AM) | 7:59 | 7:25 | 6:31 | 5:27 | 4:38 | 4:16 | 4:32 | 5:10 | 5:53 | 6:36 | 7:23 | 7:57 |
| Sunset (PM) | 4:37 | 5:21 | 6:05 | 6:50 | 7:32 | 8:01 | 7:56 | 7:15 | 6:13 | 5:11 | 4:25 | 4:12 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 8.7 | 7:59 | 4:37 |
| Feb | 9.9 | 7:25 | 5:21 |
| Mar | 11.6 | 6:31 | 6:05 |
| Apr | 13.3 | 5:27 | 6:50 |
| May | 14.9 | 4:38 | 7:32 |
| Jun | 15.7 | 4:16 | 8:01 |
| Jul | 15.4 | 4:32 | 7:56 |
| Aug | 14.1 | 5:10 | 7:15 |
| Sep | 12.4 | 5:53 | 6:13 |
| Oct | 10.6 | 6:36 | 5:11 |
| Nov | 9.1 | 7:23 | 4:25 |
| Dec | 8.3 | 7:57 | 4:12 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
West Lake Sammamish averages about 7 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 3 and 16 days.
The sunnier stretch runs 3.8 months, from around Jun 22 to Oct 14. The sunniest month is July, with roughly 14 sunny days (mixed).
The greyest month is April, down near 4 sunny days — about 70% fewer than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 5 | 5 | 4 | 4 | 6 | 6 | 14 | 14 | 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 | 4 | Gloomy |
| Apr | 4 | Gloomy |
| May | 6 | Gloomy |
| Jun | 6 | Gloomy |
| Jul | 14 | Mixed |
| Aug | 14 | 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 West Lake Sammamish, the air stays dry or comfortable essentially all year. Even in August, the muggiest month, it feels humid or worse only about 4% 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 | 88 | 64 | 62 | 84 | 98 | 100 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 0 | 2 | 11 | 32 | 34 | 15 | 2 | 0 | 0 |
| Humid (%) | 0 | 0 | 0 | 0 | 0 | 1 | 3 | 4 | 1 | 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 | 88 | 11 | 1 |
| Jul | 64 | 32 | 3 |
| Aug | 62 | 34 | 4 |
| Sep | 84 | 15 | 1 |
| 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 West Lake Sammamish is typically calm, near 5 mph, and varies little with the seasons.
The windier part of the year lasts 5.9 months, from around Oct 19 to Apr 15. The windiest month is December, averaging about 6 mph (calm).
The calmer part of the year runs from around Apr 16 to Oct 18, 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 West Lake Sammamish
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
West Lake Sammamish's rainy season runs October–April, when most of the year's rain falls.
Best time to visit West Lake Sammamish
To characterize how pleasant the weather is in West Lake Sammamish throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around early September, West Lake Sammamish 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 West Lake Sammamish 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) | 0.8 | 1.5 | 2.2 | 3.4 | 5.1 | 5.9 | 7.6 | 7.8 | 6.6 | 3.9 | 1.6 | 0.6 |
| Rating | poor | poor | poor | poor | fair | good | ideal | ideal | good | fair | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 0.8 | poor |
| Feb | 1.5 | poor |
| Mar | 2.2 | poor |
| Apr | 3.4 | poor |
| May | 5.1 | fair |
| Jun | 5.9 | good |
| Jul | 7.6 | ideal |
| Aug | 7.8 | ideal |
| Sep | 6.6 | good |
| Oct | 3.9 | fair |
| Nov | 1.6 | poor |
| Dec | 0.6 | 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 West Lake Sammamish for hot-weather activities is from mid July to late August, with a peak score in the first week of August.
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 West Lake Sammamish, 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 74°F), the essentials are light clothes and sun protection. In the cold season around December (highs near 44°F), pack a warm layer, a heavy coat and rain gear.
In August, West Lake Sammamish sees daytime highs around 74°F and nights near 54°F. Worth packing: light clothes and sun protection. About 6 days see rain.
UV index (midday) in West Lake Sammamish 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 West Lake Sammamish 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 17 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 West Lake Sammamish
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 4.5 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 | 6.5 | 4 | 0 | 0 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 0 | 2.5 | 0 | 4.5 | 1 | 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 | 2.5 |
| Jun | 7 | 0 |
| Jul | 8.5 | 4.5 |
| Aug | 6.5 | 1 |
| Sep | 4 | 0 |
| Oct | 0 | 0 |
| Nov | 0 | 0 |
| Dec | 0 | 0 |
Air quality in West Lake Sammamish 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 West Lake Sammamish is worst in September — around 22 µg/m³ PM2.5 (moderate), about 3.4× the cleanest month (December, 7 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 | 9 | 12 | 12 | 11 | 10 | 10 | 18 | 22 | 12 | 8 | 7 |
| Level | Good | Good | Moderate | Good | Good | Good | Good | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 8 | Good |
| Feb | 9 | Good |
| Mar | 12 | Moderate |
| Apr | 12 | Good |
| May | 11 | Good |
| Jun | 10 | Good |
| Jul | 10 | Good |
| Aug | 18 | Moderate |
| Sep | 22 | Moderate |
| Oct | 12 | Good |
| Nov | 8 | Good |
| Dec | 7 | Good |
Growing season
West Lake Sammamish is mild enough that a frost-free day stays more likely than not even in midwinter. Nights are reliably above freezing from about March 27 to October 29 (217 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 | 73 | 85 | 96 | 100 | 100 | 100 | 100 | 100 | 96 | 81 | 68 |
| Frost nights | 31 | 28 | 30 | 0 | 0 | 0 | 0 | 0 | 0 | 4 | 30 | 31 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 70 | 31 |
| Feb | 73 | 28 |
| Mar | 85 | 30 |
| Apr | 96 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 96 | 4 |
| Nov | 81 | 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. West Lake Sammamish banks about 1,590 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 | 7 | 141 | 262 | 430 | 438 | 266 | 46 | 0 | 0 |
| Growing degree days (°F·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 0 |
| Apr | 7 |
| May | 141 |
| Jun | 262 |
| Jul | 430 |
| Aug | 438 |
| Sep | 266 |
| Oct | 46 |
| 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.
West Lake Sammamish receives about 3.4 kWh/m² a day of solar energy on average — moderate — with a clear seasonal swing between 0.9 and 6.2 kWh/m².
The brighter stretch of the year lasts 6.0 months, from around Mar 27 to Sep 25. The brightest month is July, averaging about 6.1 kWh/m² (intense).
The dimmest month is December, down near 0.9 kWh/m² — roughly 85% 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 | 3.0 | 4.3 | 5.3 | 5.5 | 6.2 | 5.4 | 4.1 | 2.3 | 1.2 | 0.9 |
| 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 | 3.0 | Moderate |
| Apr | 4.3 | Bright |
| May | 5.3 | Bright |
| Jun | 5.5 | Bright |
| Jul | 6.2 | Intense |
| Aug | 5.4 | Bright |
| Sep | 4.1 | Bright |
| Oct | 2.3 | Moderate |
| Nov | 1.2 | Dim |
| Dec | 0.9 | Dim |
Where is West Lake Sammamish?
West Lake Sammamish sits at 47.6°N, 122.1°W, 30 ft above sea level, in United States. The nearest listed city is City of Sammamish, 3.7 mi away.
Topography around West Lake Sammamish
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of West Lake Sammamish.
Within 2 miles, the terrain around West Lake Sammamish has significant variations in elevation — a maximum elevation change of 1,076 ft around an average of 272 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,005 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,695 ft.
The land around West Lake Sammamish is covered by trees (52%) and water (32%) within 2 miles, trees (66%) within 10 miles, and trees (76%) 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 West Lake Sammamish (47.5776°, -122.1012°, elevation 30 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. 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).