USDA Hardiness Zone 8b
Frost Dates for 98273 — Mount Vernon, Washington
NOAA 1991–2020 normals from Mt Vernon 3 WNW, WA (14 ft), 2 miles northwest.
Updated
In Mount Vernon, the last spring frost (32°F) is around March 24 in half of years and has passed by April 14 in nine years out of ten. The first fall frost comes around November 3, as early as October 12 one year in ten, leaving a typical freeze-free season of 224 days (NOAA, Mt Vernon 3 WNW, WA).
- Last spring frost
- March 24
- First fall frost
- November 3
- Growing season
- 224 days
- Hardiness zone
- 8b
50% probability
50% probability
freeze-free, 50%
15 to 20°F (-9.4 to -6.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 33%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
6 of 18 observed
NOAA normal
Frost risk by date in Mount Vernon
Half of springs at Mt Vernon 3 WNW, WA see their last 32°F night by March 24; only one in ten is past it by March 3, and one in ten still has one after April 14. Planting tender crops after April 1 leaves a 30% risk of a frost on them, after April 7 20%, and after April 14 10%. The 21 days between the even-odds date and the one-in-ten date is wider than at 65% of the 113 Washington stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by November 3 in half of years, as early as October 12 one year in ten, and holds off past November 25 one year in ten. A hard freeze of 28°F follows 22 days later, around November 25; in spring the one-in-ten date for 28°F is March 17, 28 days before the 32°F one. The freeze-free season lasts 224 days in a typical year, longer than at 77% of the 113 Washington stations; it reaches 256 days one year in ten and falls short of 196 one year in ten. On average 46 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 25 days longer, to about April 18, and return around October 16. Nights of 24°F, cold enough to damage hardier plants, come in 92% of winters and 16°F in 25%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 29 | Apr 4 | Apr 10 | Apr 15 | Apr 18 | Apr 22 | Apr 27 | Apr 30 | May 5 |
| 32°F | Mar 3 | Mar 10 | Mar 15 | Mar 20 | Mar 24 | Mar 28 | Apr 1 | Apr 7 | Apr 14 |
| 28°F | Jan 23 | Feb 10 | Feb 18 | Feb 23 | Feb 27 | Mar 1 | Mar 6 | Mar 12 | Mar 17 |
| 24°F92% of yrs | Dec 19 | Jan 4 | Jan 15 | Jan 27 | Feb 3 | Feb 12 | Feb 19 | Feb 24 | Feb 28 |
| 20°F57% of yrs | Dec 9 | Dec 21 | Dec 31 | Jan 4 | Jan 12 | Jan 20 | Jan 31 | Feb 11 | Feb 21 |
| 16°F25% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 29 | Oct 3 | Oct 7 | Oct 11 | Oct 16 | Oct 19 | Oct 24 | Oct 30 | Nov 6 |
| 32°F | Oct 12 | Oct 21 | Oct 26 | Oct 31 | Nov 3 | Nov 8 | Nov 13 | Nov 19 | Nov 25 |
| 28°F | Oct 31 | Nov 7 | Nov 13 | Nov 19 | Nov 25 | Nov 30 | Dec 4 | Dec 13 | Dec 23 |
| 24°F92% of yrs | Nov 13 | Nov 23 | Dec 1 | Dec 6 | Dec 15 | Dec 22 | Dec 30 | Jan 8 | Jan 29 |
| 20°F57% of yrs | Nov 24 | Dec 5 | Dec 12 | Dec 20 | Dec 28 | Jan 1 | Jan 9 | Jan 24 | Feb 9 |
| 16°F25% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Mt Vernon 3 WNW, WA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 98273 →Compare Mount Vernon with another place →
Weather by month in Mount Vernon
August is the warmest month at Mt Vernon 3 WNW, WA, averaging 75°F by day and 53°F at night; December is the coldest at 46°F and 35°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 89% of years and April still brings one in 32% of years.
Warmth for growing adds up to 1,764 growing degree days a year (base 50°F), fewer than at 70% of the 113 Washington stations. 31% of them (543) have built up by the end of June, and August adds the most, 439.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 47 | 35 | 98% | 12 | 7 |
| Feb | 50 | 35 | 94% | 10 | 3 |
| Mar | 54 | 38 | 89% | 5 | 15 |
| Apr | 58 | 41 | 32% | 1 | 44 |
| May | 65 | 47 | 0% | <1 | 183 |
| Jun | 69 | 51 | 0% | 0 | 291 |
| Jul | 73 | 54 | 0% | 0 | 415 |
| Aug | 75 | 53 | 0% | 0 | 439 |
| Sep | 69 | 49 | 3% | <1 | 262 |
| Oct | 59 | 43 | 40% | 1 | 83 |
| Nov | 51 | 39 | 90% | 7 | 19 |
| Dec | 46 | 35 | 99% | 10 | 3 |
Monthly normals 1991–2020 at Mt Vernon 3 WNW, WA (14 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Sedro-Woolley, WA, 8 miles northeast of Mount Vernon, has a last frost 3 days later (March 27), a first frost 3 days later (November 6).
When it snows in Mount Vernon, Washington
Measurable snow is rare here: only 6 of 18 winters from 1991 to 2020 recorded 0.1 inch or more at Anacortes, WA, 13.7 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 98273
| When | What to do |
|---|---|
| January 13 – January 27 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 27 – February 10 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 24 – March 10 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 24 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 11 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 20 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 3 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 98273 is 2 miles from Mt Vernon 3 WNW, WA, which stands at 14 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 98273 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Washington →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.