USDA Hardiness Zone 7b
Frost Dates for 73093 — Washington, Oklahoma
NOAA 1991–2020 normals from Norman 3SSE, OK (1,128 ft), 7 miles northeast.
Updated
In Washington, the last spring frost (32°F) is around April 3 in half of years and has passed by April 18 in nine years out of ten. The first fall frost comes around November 3, as early as October 21 one year in ten, leaving a typical freeze-free season of 212 days (NOAA, Norman 3SSE, OK).
- Last spring frost
- April 3
- First fall frost
- November 3
- Growing season
- 212 days
- Hardiness zone
- 7b
50% probability
50% probability
freeze-free, 50%
5 to 10°F (-15.0 to -12.2°C) coldest night
- First snow
- December 23
- Last snow
- February 13
- Winters with snow
- 96%
- Snow per year
- 4.1"
median, 1991–2020
median, 1991–2020
23 of 24 observed
NOAA normal
Frost risk by date in Washington
Half of springs at Norman 3SSE, OK see their last 32°F night by April 3; only one in ten is past it by March 19, and one in ten still has one after April 18. Planting tender crops after April 9 leaves a 30% risk of a frost on them, after April 14 20%, and after April 18 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 86% of the 114 Oklahoma stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 3 in half of years, as early as October 21 one year in ten, and holds off past November 17 one year in ten. A hard freeze of 28°F follows 9 days later, around November 12; in spring the one-in-ten date for 28°F is April 7, 11 days before the 32°F one. The freeze-free season lasts 212 days in a typical year, longer than at 54% of the 114 Oklahoma stations; it reaches 234 days one year in ten and falls short of 191 one year in ten. On average 77 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 11 days longer, to about April 14, and return around October 25. Severe cold of 16°F or below comes in 99% of winters, usually between December 19 and February 17.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 30 | Apr 4 | Apr 7 | Apr 10 | Apr 14 | Apr 17 | Apr 20 | Apr 23 | Apr 28 |
| 32°F | Mar 19 | Mar 25 | Mar 29 | Mar 31 | Apr 3 | Apr 6 | Apr 9 | Apr 14 | Apr 18 |
| 28°F | Mar 5 | Mar 12 | Mar 16 | Mar 20 | Mar 23 | Mar 28 | Mar 31 | Apr 3 | Apr 7 |
| 24°F | Feb 24 | Mar 1 | Mar 5 | Mar 9 | Mar 11 | Mar 14 | Mar 18 | Mar 23 | Mar 29 |
| 20°F | Feb 8 | Feb 17 | Feb 22 | Feb 27 | Mar 2 | Mar 5 | Mar 9 | Mar 13 | Mar 19 |
| 16°F99% of yrs | Jan 19 | Jan 30 | Feb 6 | Feb 11 | Feb 17 | Feb 23 | Mar 1 | Mar 4 | Mar 10 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 11 | Oct 17 | Oct 20 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 2 | Nov 6 |
| 32°F | Oct 21 | Oct 25 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 17 |
| 28°F | Oct 27 | Nov 1 | Nov 5 | Nov 8 | Nov 12 | Nov 15 | Nov 17 | Nov 21 | Nov 27 |
| 24°F | Nov 4 | Nov 10 | Nov 14 | Nov 18 | Nov 21 | Nov 25 | Nov 29 | Dec 3 | Dec 9 |
| 20°F | Nov 13 | Nov 20 | Nov 25 | Nov 29 | Dec 2 | Dec 6 | Dec 11 | Dec 17 | Dec 25 |
| 16°F99% of yrs | Nov 26 | Dec 2 | Dec 7 | Dec 13 | Dec 19 | Dec 25 | Dec 31 | Jan 5 | Jan 15 |
Freeze probabilities 1991–2020 at Norman 3SSE, OK, 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 73093 →Compare Washington with another place →
Weather by month in Washington
July is the warmest month at Norman 3SSE, OK, averaging 93°F by day and 71°F at night; January is the coldest at 50°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 59% of years.
Warmth for growing adds up to 5,109 growing degree days a year (base 50°F), fewer than at 56% of the 114 Oklahoma stations. 38% of them (1,927) have built up by the end of June, and July adds the most, 987. Precipitation totals 37.6 inches a year, most in May (5.1") and least in January (1.4"); May to September bring 56% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 50 | 28 | 1.4 | 100% | 22 | 18 |
| Feb | 54 | 31 | 1.6 | 100% | 17 | 47 |
| Mar | 63 | 40 | 2.8 | 99% | 7 | 152 |
| Apr | 71 | 48 | 3.5 | 59% | 1 | 316 |
| May | 79 | 58 | 5.1 | 0% | 0 | 577 |
| Jun | 87 | 67 | 4.8 | 0% | 0 | 817 |
| Jul | 93 | 71 | 3.7 | 0% | 0 | 987 |
| Aug | 92 | 70 | 3.6 | 0% | 0 | 965 |
| Sep | 84 | 62 | 3.7 | 0% | 0 | 696 |
| Oct | 74 | 50 | 3.4 | 38% | 1 | 385 |
| Nov | 62 | 39 | 2.0 | 99% | 8 | 123 |
| Dec | 52 | 31 | 2.0 | 100% | 20 | 25 |
Monthly normals 1991–2020 at Norman 3SSE, OK (1,128 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, Purcell 2 SW, OK, 9 miles southeast of Washington, has a last frost 1 day later (April 4), a first frost 1 day earlier (November 2), a season 2 days shorter.
When it snows in Washington, Oklahoma
The first measurable snow (0.1 inch or more) in Washington usually arrives around December 23, and the last of the season around February 13. Those are the middle dates across the winters of 1991–2020 at Norman 3SSE, OK, 6.9 miles away: half of years saw snow earlier, half later. Snow fell in 96% of those winters. The last 32°F night of spring typically comes 49 days after the last snow.
Planting calendar for 73093
| When | What to do |
|---|---|
| January 23 – February 6 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 6 – February 20 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 6 – March 20 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 3 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 73093 is 7 miles from Norman 3SSE, OK, which stands at 1,128 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 73068 (Noble). The 2023 USDA Plant Hardiness Zone Map lists ZIP 73093 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°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.