USDA Hardiness Zone 8a
Frost Dates for 20037 — Washington, District of Columbia
NOAA 1991–2020 normals from Washington Reagan Airport, VA (10 ft), 4 miles south.
Updated
In Washington, the last spring frost (32°F) is around March 24 in half of years and has passed by April 6 in nine years out of ten. The first fall frost comes around November 18, as early as November 5 one year in ten, leaving a typical freeze-free season of 241 days (NOAA, Washington Reagan Airport, VA).
- Last spring frost
- March 24
- First fall frost
- November 18
- Growing season
- 241 days
- Hardiness zone
- 8a
50% probability
50% probability
freeze-free, 50%
10 to 15°F (-12.2 to -9.4°C) coldest night
- First snow
- December 19
- Last snow
- March 4
- Winters with snow
- 100%
- Snow per year
- 13.7"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Washington
Half of springs at Washington Reagan Airport, VA see their last 32°F night by March 24; only one in ten is past it by March 7, and one in ten still has one after April 6. Planting tender crops after March 30 leaves a 30% risk of a frost on them, after April 2 20%, and after April 6 10%. The 13 days between the even-odds date and the one-in-ten date measure how much the end of the frost season moves from year to year.
In fall the first 32°F night comes by November 18 in half of years, as early as November 5 one year in ten, and holds off past December 6 one year in ten. A hard freeze of 28°F follows 15 days later, around December 3; in spring the one-in-ten date for 28°F is March 26, 11 days before the 32°F one. The freeze-free season lasts 241 days in a typical year; it reaches 265 days one year in ten and falls short of 220 one year in ten. On average 60 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 10 days longer, to about April 3, and return around November 6. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 78%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 20 | Mar 25 | Mar 29 | Apr 1 | Apr 3 | Apr 5 | Apr 7 | Apr 11 | Apr 14 |
| 32°F | Mar 7 | Mar 14 | Mar 17 | Mar 21 | Mar 24 | Mar 27 | Mar 30 | Apr 2 | Apr 6 |
| 28°F | Feb 23 | Mar 1 | Mar 5 | Mar 8 | Mar 12 | Mar 15 | Mar 18 | Mar 21 | Mar 26 |
| 24°F | Feb 8 | Feb 16 | Feb 22 | Feb 27 | Mar 2 | Mar 5 | Mar 9 | Mar 14 | Mar 19 |
| 20°F98% of yrs | Jan 16 | Jan 29 | Feb 3 | Feb 8 | Feb 15 | Feb 20 | Feb 26 | Mar 2 | Mar 7 |
| 16°F78% of yrs | Jan 9 | Jan 15 | Jan 21 | Jan 27 | Jan 31 | Feb 3 | Feb 9 | Feb 16 | Feb 24 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 26 | Oct 30 | Nov 2 | Nov 4 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 20 |
| 32°F | Nov 5 | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | Nov 25 | Nov 30 | Dec 6 |
| 28°F | Nov 14 | Nov 21 | Nov 26 | Nov 30 | Dec 3 | Dec 6 | Dec 11 | Dec 17 | Dec 24 |
| 24°F | Dec 1 | Dec 7 | Dec 11 | Dec 17 | Dec 22 | Dec 25 | Dec 30 | Jan 3 | Jan 12 |
| 20°F98% of yrs | Dec 13 | Dec 21 | Dec 26 | Jan 1 | Jan 4 | Jan 8 | Jan 13 | Jan 20 | Jan 29 |
| 16°F78% of yrs | Dec 26 | Jan 1 | Jan 6 | Jan 10 | Jan 14 | Jan 18 | Jan 24 | Jan 28 | Feb 5 |
Freeze probabilities 1991–2020 at Washington Reagan Airport, VA, 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 20037 →Compare Washington with another place →
Weather by month in Washington
July is the warmest month at Washington Reagan Airport, VA, averaging 90°F by day and 72°F at night; January is the coldest at 45°F and 30°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 25% of years.
Warmth for growing adds up to 4,709 growing degree days a year (base 50°F). 36% of them (1,701) have built up by the end of June, and July adds the most, 961. Precipitation totals 41.8 inches a year, most in July (4.3") and least in February (2.6"); May to September bring 47% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 45 | 30 | 2.9 | 100% | 20 | 12 |
| Feb | 48 | 32 | 2.6 | 100% | 15 | 18 |
| Mar | 57 | 39 | 3.5 | 95% | 8 | 81 |
| Apr | 68 | 48 | 3.2 | 25% | 1 | 267 |
| May | 77 | 58 | 3.9 | 0% | 0 | 535 |
| Jun | 85 | 68 | 4.2 | 0% | 0 | 789 |
| Jul | 90 | 72 | 4.3 | 0% | 0 | 961 |
| Aug | 88 | 71 | 3.3 | 0% | 0 | 911 |
| Sep | 81 | 64 | 3.9 | 0% | 0 | 672 |
| Oct | 69 | 52 | 3.7 | 3% | 0 | 343 |
| Nov | 58 | 42 | 2.9 | 80% | 4 | 98 |
| Dec | 49 | 35 | 3.4 | 99% | 13 | 23 |
Monthly normals 1991–2020 at Washington Reagan Airport, VA (10 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, Dalecarlia Rsvr, MD, 4 miles northwest of Washington, has a last frost 16 days later (April 9), a first frost 18 days earlier (October 31), a season 39 days shorter.
When it snows in Washington, District of Columbia
The first measurable snow (0.1 inch or more) in Washington usually arrives around December 19, and the last of the season around March 4. Those are the middle dates across the winters of 1991–2020 at Washington Reagan Airport, VA, 3.7 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 20 days after the last snow.
Planting calendar for 20037
| 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 26 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 4 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 18 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 20037 is 4 miles from Washington Reagan Airport, VA, which stands at 10 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 17 other ZIP codes share the station; its figures are presented in full for 22204 (Arlington). The 2023 USDA Plant Hardiness Zone Map lists ZIP 20037 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°C) over 1991–2020; a zone describes winter lows, not frost dates.
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.