Mount Vernon, Washington climate: Normal weather by month, frost dates and records
Mount Vernon's normal year runs from 35°F December nights to 75°F August afternoons. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.8°C, December lows of 2°C, August highs of 24°C.
- NOAA stationMount Vernon (3 mi WNW)
- Station IDUSC00455678
- Location48.44°N 122.39°W
- Elevation14 ft (4 m)
- Population35,344
On October 14, the normal high in Mount Vernon is 60°F and the normal low 44°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Mount Vernon.
- Jan 47° 35°
- Feb 50° 35°
- Mar 54° 38°
- Apr 58° 41°
- May 65° 47°
- Jun 69° 51°
- Jul 73° 54°
- Aug 75° 53°
- Sep 69° 49°
- Oct 59° 43°
- Nov 51° 39°
- Dec 46° 35°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Mount Vernon each month?
August is the warmest month, with normal highs of 75°F; December the coldest, with normal lows of 35°F.
| Month | High | Low | Mean | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|
| January | 47°F | 35°F | 41.1°F | – | <1 | 12 | 8 h 40 min |
| February | 50°F | 35°F | 42.2°F | – | <1 | 10 | 10 h 10 min |
| March | 54°F | 38°F | 45.8°F | – | <1 | 5 | 11 h 50 min |
| April | 58°F | 41°F | 49.8°F | – | <1 | 1 | 13 h 40 min |
| May | 65°F | 47°F | 55.7°F | – | <1 | <1 | 15 h 10 min |
| June | 69°F | 51°F | 59.7°F | – | <1 | <1 | 16 h |
| July | 73°F | 54°F | 63.4°F | – | <1 | <1 | 15 h 50 min |
| August | 75°F | 53°F | 64.1°F | – | <1 | <1 | 14 h 20 min |
| September | 69°F | 49°F | 58.7°F | – | <1 | <1 | 12 h 40 min |
| October | 59°F | 43°F | 51.3°F | – | <1 | 1 | 11 h |
| November | 51°F | 39°F | 45.0°F | – | <1 | 7 | 9 h 20 min |
| December | 46°F | 35°F | 40.6°F | – | <1 | 10 | 8 h 20 min |
| Year (annual) | 60°F | 43°F | 51.5°F | – | <1 | 46 |
The same normals in °C and millimetres
| Month | High | Low | Mean |
|---|---|---|---|
| January | 8°C | 2°C | 5.1°C |
| February | 10°C | 2°C | 5.7°C |
| March | 12°C | 3°C | 7.7°C |
| April | 15°C | 5°C | 9.9°C |
| May | 18°C | 8°C | 13.2°C |
| June | 20°C | 10°C | 15.4°C |
| July | 23°C | 12°C | 17.4°C |
| August | 24°C | 12°C | 17.8°C |
| September | 20°C | 9°C | 14.8°C |
| October | 15°C | 6°C | 10.7°C |
| November | 11°C | 4°C | 7.2°C |
| December | 8°C | 2°C | 4.8°C |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Sedro-Woolley (8 miles away), gets 6 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00455678; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Mount Vernon?
Normal highs sit between 65°F and 85°F in June, July, August and September.
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00455678.
When is the last frost in Mount Vernon?
In Mount Vernon, the last spring frost (32°F) comes after March 24 in half of years and after April 14 in one year in ten; the first autumn frost comes before November 3 in half of years and before October 12 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- March 241 year in 10 after April 14; 9 in 10 after March 3
- First autumn frost, half of years before
- November 31 year in 10 before October 12; 9 in 10 before November 25
NOAA puts the median frost-free season at 224 days, and the season without a hard freeze (28°F) at 273 days.
A hard freeze (28°F) comes after February 27 in half of springs and before November 25 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Mount Vernon in zone 8b in ZIP code 98273, the nearest ZIP area.
Frost dates for every NOAA station in Washington · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00455678; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Mount Vernon?
In a normal year in Mount Vernon, a 90°F day is rare and 46 nights fall to 32°F or colder.
- Days at 90°F or more
- fewer than 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 46a normal year
- Days that stay below freezing
- 3high of 32°F or less
The highest temperature in this station's record (since 1956) is 98°F, on August 9, 1960; the lowest is −4°F, on January 26, 1957.
The wettest calendar year on that record is 1990, with 47.20 in; the snowiest season is 1968–69, with 17.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00455678; records: ACIS (NOAA Regional Climate Centers), station USC00455678. Records use complete months only; a month missing more than three days is left out.
How sunny is Mount Vernon?
Over a year 70% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Mount Vernon, 3.5 kWh per square metre a day. July is the sunniest month (82%) and December the cloudiest (51%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 52% | 1.0 |
| February | 61% | 1.9 |
| March | 61% | 2.9 |
| April | 67% | 4.3 |
| May | 71% | 5.5 |
| June | 72% | 6.0 |
| July | 82% | 6.5 |
| August | 81% | 5.5 |
| September | 76% | 3.9 |
| October | 64% | 2.2 |
| November | 55% | 1.1 |
| December | 51% | 0.8 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Mount Vernon need?
A normal year in Mount Vernon brings 4,986 heating degree days, 7% fewer than the median U.S. place (5,373), and 64 cooling degree days, 93% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,764 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 742 | 0 |
| February | 637 | 0 |
| March | 594 | 0 |
| April | 455 | 0 |
| May | 289 | 1 |
| June | 165 | 6 |
| July | 75 | 25 |
| August | 57 | 30 |
| September | 191 | 2 |
| October | 426 | 0 |
| November | 600 | 0 |
| December | 756 | 0 |
| Year (annual) | 4,986 | 64 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00455678. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
How does Mount Vernon's climate compare?
Mount Vernon is warmer than 71 of the other 95 places with their own NOAA record in Washington. Across the 7,247 U.S. stations with normals, its annual mean of 51.5°F is warmer than 47%.
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers.
Which places near Mount Vernon share this climate record?
6 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Burlington, WA10,945 people · 3 mi NE
- Lake Ketchum, WA1,088 people · 11 mi S
- La Conner, WA994 people · 6 mi SW
- Bay View, WA626 people · 5 mi NW
- Bow, WA584 people · 8 mi N
- Conway, WA44 people · 7 mi S
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Mount Vernon's climate
What is the coldest month in Mount Vernon?
December, with a normal high of 46°F and a normal low of 35°F. The warmest is August (75°F by day, 53°F at night).
Does it snow in Mount Vernon?
Yes. NOAA publishes no 1991-2020 snowfall normal for Mount Vernon's NOAA station; the nearest record that keeps one, Sedro-Woolley (8 miles away), records 6 inches of snow in a normal year.
What plant hardiness zone is Mount Vernon in?
The USDA's 2023 map puts Mount Vernon in zone 8b in ZIP code 98273, the nearest ZIP area.
How late can frost come in Mount Vernon?
In half of years the last 32°F night comes after March 24; in one year in ten it comes after April 14. Waiting until April 14 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Washington climateThe statewide normals and every place in the state
- Sedro-Woolley, WA8 miles from this station, 51.3°F a year
- Anacortes, WA12 miles from this station, 52.8°F a year
- Whidbey Island Naval Air Station, WA14 miles from this station, 52.1°F a year
- Arlington, WA21 miles from this station, 49.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made