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Mercer Island, Washington Weather

Fireweed Ignites. Day 15 of summer. Read this microseason across nine climate regions →

Mercer Island weather forecast — hour by hour, 7-day outlook, NOAA radar

Mercer Island, WA
Sunday, July 5 at 1:00 AM
56
°
Overcast
Feels like
53°
Humidity
74%
Wind
7 mph
Sunrise
10:18 PM
Sunset
2:08 PM
Mercer Island, WA
Hour by hour · 24h
24-Hour ForecastMercer Island, WA: 24-hour forecast. Temperatures range from 53 to 76 degrees Fahrenheit.
L 53°H 76°
Mercer Island, WA
7-day forecast
  1. Today
    Jul 5
    Overcast
    —
    —
    76°53°—
  2. Monday
    Jul 6
    Overcast
    —
    —
    82°54°+6°
  3. Tuesday
    Jul 7
    Overcast
    —
    —
    83°55°+1°
  4. Wednesday
    Jul 8
    Light Drizzle
    —
    0.01″
    69°54°-14°
  5. Thursday
    Jul 9
    Clear
    —
    —
    79°49°+10°
  6. Friday
    Jul 10
    Clear
    —
    —
    81°53°+2°
  7. Saturday
    Jul 11
    Overcast
    —
    —
    82°55°+1°
Mercer Island, WA
Next 24 hours · Cool now
45°63°80°6p12a6a12pnow 56°high 76°low 53°
Mercer Island, WA
Anemometer · 24h winds · from true
NESW
From · True
ENE
059° · veering 104°
Direction
ENE
059°
Sustained
7
mph
Gust
16
mph
Peak 24h
16
avg 4
Beaufort · 2 · LIGHT BRZ
0
CALM
<1
1
LIGHT AIR
1–3
2
LIGHT BRZ
4–7
3
GENTLE BRZ
8–12
4
MOD BRZ
13–18
5
FRESH BRZ
19–24
6
STRONG BRZ
25–31
7
NEAR GALE
32–38
24h · sust vs gust · mph
avg 4 · pk 16 @ 1:00a
01020MPHB1B2B3B4B5-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 175SUSTGUST
−24h−18h−12h−6hnow
Light breeze veering 104° from the ene.
Mercer Island, WA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
1017.9
+0.5 mb in 3h · steady · 30.06 inHg
Now
1017.9
mb
3h
+0.5
mb
12h
-1.0
mb
24h
+1.6
mb
Regime · FAIR
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 1016–1019
1010RAIN|CHG1015CHG|FAIR10201025FAIR|DRY-21h-18h-15h-12h-9h-6h-3h-24hNOW1018.91016.31017.9
−24h−18h−12h−6hnow
Fair, steady air — a quiet anticyclone holds the sky.
Mercer Island, WA
Air quality
31
AQI
Good
↓-7 in 6h

AQI 31 (Good), driven by PM2.5. AQI down 7 over the last 6 hours (gradual decline).

OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.

PM 2.5DRIVERGood
3.8μg/m³
PM 10Good
5μg/m³
NO₂Good
11μg/m³
OzoneGood
37μg/m³
UV IndexLow
0.0

Trends

Seven days of AQI and PM2.5.

Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).

7-DAY AQI TREND50100SUNMONTUEWEDTHUFRISATSUN7-DAY PM2.5 TREND · μg/m³300
Mercer Island, WA
Sky cover · visibility · 24h
Cloud cover
86%
MOSTLY CLOUDY
100%0%−24h−18h−12h−6hnow
Visibility
40.2mi
UNLIMITED
65 mi0 mi−24h−18h−12h−6hnow
Earth · GOES-19 ABI
Full Disk · Visible · GeoColor
GOES-19 full disk Visible · GeoColor
True-color daytime, blue/IR sandwich at night
08:00 UTC · Mercer Island, WA · NOAA NESDIS / STAR · up to 10848 px
Continental US · GOES-19 ABI
CONUS Sector · Visible · GeoColor
GOES-19 CONUS Visible · GeoColor
Daytime true-color, blue-light/IR sandwich at night
08:00 UTC · Mercer Island, WA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Mercer Island, WA
Satellite · infrared · animated
Mercer Island, WA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Mercer Island, WA
Almanac · Sunday, July 5
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
Civil dawn
4:38 AM
Sunrise
10:18 PM
Daylight
15h 50m
Sunset
2:08 PM
Civil dusk
9:50 PM
Planting note
Harvest early potatoes. Begin drying onions on the surface.
Mercer Island, WA
The moon
Waning Gibbous
74% illuminated
Moonrise
11:35 PM
Moonset
11:24 AM
In sign
♓︎ Pisces
Mercer Island, WA
Microseason
Jul 1–5

Fireweed Ignites

weather
Jan 151% of the yearDec 31

Read this microseason across nine climate regions →

Mercer Island at a glance

  • Today vs. normal: 8°F below the seasonal normal for this latitude
  • Last frost: May 31 (climatological average for this latitude)
  • Microseason: Jul 1–5
  • Planting window: Harvest early potatoes. Begin drying onions on the surface.

ZIP code: 98040

15-Day Forecast — Mercer Island

  1. Sun76°53°0%
  2. Mon82°54°0%
  3. Tue83°55°0%
  4. Wed69°54°6%
  5. Thu79°49°5%
  6. Fri81°53°2%
  7. Sat82°55°8%
  8. Sun79°53°4%
  9. Mon84°51°5%
  10. Tue85°55°4%
  11. Wed84°58°5%
  12. Thu87°59°10%
  13. Fri91°61°3%
  14. Sat77°58°10%
  15. Sun83°54°3%

Forecast data from Open-Meteo (CC BY 4.0).

Right now in the garden

Peak growing season

As of July 5, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.

January 1–5: The Year's Deep Silence.January 6–10: The First Pressure Shift.January 11–15: The Lengthening.January 16–20: The Crows Begin.January 21–25: Skunk Cabbage Wakens.January 26–31: The Fog Deepens.February 1–5: The Sap Stirs.February 6–10: East Wind Weakens the Marine Layer.February 11–15: Thrush Song at First Light.February 16–20: The Salmon Remember.February 21–25: The Soil Awakens.February 26–28: Mist Begins to Linger.March 1–5: The Buds Emerge.March 6–10: The Small Lives Stir.March 11–15: The Spring Salmon Peak.March 16–20: Alder Catkins Dust the Air.March 21–25: Equinox Fog Clears.March 26–31: Salmonberry First Bloom.April 1–5: Thunder Rolls Down the Valleys.April 6–10: Swallows Arrive at the Bridges.April 11–15: Geese Turn Their Faces North.April 16–20: Rainbows Arc Above the Cascades.April 21–25: Reeds Rise from the Wetlands.April 26–30: Frost Releases the Garden.May 1–5: Warblers Flood the Canopy.May 6–10: Frogs Sing at Twilight.May 11–15: Earthworms Rise to Feed the Forest.May 16–20: Shoots and Sprouts Rise in Ranks.May 21–25: Silkworm Days—Full Canopy.May 26–31: Safflower Days—Late May Blooms.June 1–5: Rufous Hummingbirds Arrive.June 6–10: Oceanspray Towers.June 11–15: Solstice Light Crests.June 16–20: Thimbleberry Sweetens.June 21–25: Summer Solstice Stillness.June 26–30: Dry Pattern Deepens.July 1–5: Fireweed Ignites.July 6–10: Peak Hummingbird Wars.July 11–15: Red Huckleberry Ripens.July 16–20: Smoke Season Beckons.July 21–25: Dog Days Hold.July 26–31: Smoke Deepens.August 1–5: August Arrives Dimmed.August 6–10: Cool Wind Hints Return.August 11–15: Cicadas Crescendo.August 16–20: Marine layer deepens.August 21–25: First sweater morning.August 26–31: August snap arrives.September 1–5: Rivers quicken with silver.September 6–10: Dew settles thick.September 11–15: Raptors funnel through passes.September 16–20: Equinox—darkness gains.September 21–25: Fog locks the valleys.September 26–30: Geese stage southward.October 1–5: Mushroom flush deepens.October 6–10: Maples ignite orange.October 11–15: Frost's first mark.October 16–20: Oaks turn russet.October 21–25: First killing frost.October 26–31: Atmospheric rivers arrive.November 1–5: Maple and ivy turn to amber.November 6–10: Last leaves cling in quiet rain.November 11–15: First frost finds the lowlands.November 16–20: Bare branches open the winter sky.November 21–25: Heavy rains mask the stars.November 26–30: North wind clears the gloom.December 1–5: Darkness settles early.December 6–10: Winter cold locks the sky.December 11–15: The days reach their minimum.December 16–20: Ice forms at the margins.December 21–25: The sun turns at solstice.December 26–31: Year's end in silence.🌱February 14 — First skunk-cabbage spathes thaw their way up☀️March 20 — Spring equinox — day and night balance🌸April 5 — Cherry blossoms peak in the parks🐦May 10 — Warbler migration peaks along the coast✨May 25 — First fireflies scout the meadows at dusk🌞June 21 — Summer solstice — longest day🦗July 25 — Peak cicada chorus in the afternoons🌊August 18 — Warmest sea-surface temperatures of the year🍂September 22 — Autumn equinox — the slow turn❄️October 25 — First widespread frost in the suburbs🍁November 10 — Peak leaf color across the Hudson Valley🌙December 21 — Winter solstice — longest night

Microseason · July 1–5

Fireweed Ignites

Magenta fireweed spires surge from burned and cleared slopes, their blooms climbing from base upward. July's signature color claims the disturbed ground.

Day 186 of 365 · Wedge 37 of 72

The solar year drawn as a wheel of 72 five-day windows. Each wedge is one microseason; the four colored arcs mark winter, spring, summer, and autumn; the small icons sit at notable phenological events. The crimson pointer creeps clockwise as the year turns.

Planting calendar

MonthPlantHarvest
January——
February——
March——
April——
Maylettuce, peas, spinach, radisheslettuce, peas, radishes
Junelettuce, peas, spinach, radishes, tomatoes, peppers, beans, squashlettuce, peas, radishes
Julytomatoes, peppers, beans, squashtomatoes, beans, summer squash
Augusttomatoes, peppers, beans, squash, fall brassicas, garlic (overwinter), carrotstomatoes, beans, summer squash
Septemberfall brassicas, garlic (overwinter), carrotstomatoes, beans, summer squash
October—winter squash, tomatoes (last)
November——
December——

A year in weather

In Mercer Island, August runs warmest near 67°F and January coldest around 38°F, while November is the wettest month (7.9 inches) and July the driest (0.5 inches).

MonthMean tempPrecipRainy days
January38°7.5″23
February40°5.5″20
March43°5.6″23
April48°4.1″20
May55°3.1″19
June60°2.4″16
July66°0.5″7
August67°0.9″6
September60°2.4″12
October51°6.2″19
November44°7.9″23
December38°7.5″24

Regional context

By the nearest station's NOAA NCEI 1991-2020 normals, Mercer Island sees 38°F Januarys and 66°F Julys, a 28°F range, plus around 53.6 inches of precipitation across 211 days.

Cool-season fronts carry Mercer Island's rain: November logs 7.9 inches on 22.6 days, against July's 0.5 inches on 6.8 — winter does the heavy lifting in Mercer Island. That groups Mercer Island with places like Beaux Arts Village, WA, Newcastle, WA and Bellevue, WA on the same cool-season storm track.

Mercer Island's growing window opens around late-May, once Mercer Island's overnight lows stop freezing — sow peas, lettuce, spinach, and radishes. Hold Mercer Island's tender crops — tomatoes, peppers, basil — until 10-14 days past Mercer Island's last frost. Mercer Island's window closes around early-October as overnight lows return below freezing. In Mercer Island, low spots run 4-7°F colder than nearby slopes, nudging Mercer Island's frost dates a week.

Similar climates: Beaux Arts Village, WA, Newcastle, WA, Bellevue, WA, Medina, WA, Clyde Hill, WA.

Frequently asked

When does it freeze in Mercer Island?
Frost typically leaves Mercer Island by mid-May and returns to Mercer Island near mid-October.
What is the rainy season in Mercer Island?
November is the wettest month in Mercer Island, about 7.9 inches on average; the year totals roughly 54 inches.
What is the warmest month in Mercer Island?
Mercer Island peaks in August, when the mean runs near 67°F.
What is the coldest month in Mercer Island?
January is Mercer Island's coldest month, averaging about 38°F.
When can I start a vegetable garden in Mercer Island?
Around mid-May, start frost-hardy crops in Mercer Island; tomatoes and basil belong a fortnight later.
How many rainy days does Mercer Island get?
Mercer Island records around 211 days of measurable precipitation annually.
What hardiness zone is Mercer Island?
Since January in Mercer Island averages 38°F, Mercer Island's USDA zone follows that floor — confirm it by ZIP.
What is the 10-day forecast for Mercer Island?
Mercer Island's extended outlook — daily high and low temperatures and precipitation chances for each upcoming day — is in the daily forecast above.
Will it rain this week in Mercer Island?
See this week's day-by-day rain chances for Mercer Island in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Mercer Island?
Current conditions for Mercer Island and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Mercer Island forecast updated?
The Mercer Island forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Mercer Island?
Today's sunrise and sunset times for Mercer Island are in the Almanac section above, along with civil dawn, civil dusk, and day length. Day length is longest near the summer solstice and shortest near the winter solstice.
How accurate is the weather forecast for Mercer Island?
The next few days in Mercer Island's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

Set in a warm-summer Mediterranean zone, Mercer Island, Washington swings from 38°F in the heart of winter to 66°F at midsummer — a 28°F arc.

Across the year, Mercer Island collects about 54 inches of precipitation over roughly 211 days with measurable rain or snow.

Mercer Island's 28°F range, set by its 47.6°N position, drives frost timing and what thrives in Mercer Island.

All cities in Washington →

Bellevue, WA weather →

ZIP codes in Mercer Island

  • 98040

Climate normals from the Open-Meteo Climate API. Köppen approximation from NOAA NCEI U.S. Climate Regions. See methodology for data sources, editorial rules, and corrections. Maintainer: Brian Tighe.