USDA Hardiness Zone 8a
Frost Dates for 85607 — Douglas, Arizona
NOAA 1991–2020 normals from Douglas, AZ (4,040 ft), 3 miles south.
Updated
In Douglas, the last spring frost (32°F) is around March 18 in half of years and has passed by April 12 in nine years out of ten. The first fall frost comes around November 13, as early as October 27 one year in ten, leaving a typical freeze-free season of 235 days (NOAA, Douglas, AZ).
- Last spring frost
- March 18
- First fall frost
- November 13
- Growing season
- 235 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
- Rare
- Last snow
- Rare
- Winters with snow
- 25%
- Snow per year
- 0.5"
median, 1991–2020
median, 1991–2020
5 of 20 observed
NOAA normal
Frost risk by date in Douglas
Half of springs at Douglas, AZ see their last 32°F night by March 18; only one in ten is past it by February 27, and one in ten still has one after April 12. Planting tender crops after March 31 leaves a 30% risk of a frost on them, after April 5 20%, and after April 12 10%. The 25 days between the even-odds date and the one-in-ten date is wider than at 63% of the 98 Arizona 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 13 in half of years, as early as October 27 one year in ten, and holds off past November 30 one year in ten. A hard freeze of 28°F follows 12 days later, around November 25; in spring the one-in-ten date for 28°F is March 24, 19 days before the 32°F one. The freeze-free season lasts 235 days in a typical year, longer than at 52% of the 98 Arizona stations; it reaches 264 days one year in ten and falls short of 204 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 20 days longer, to about April 7, and return around November 3. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 37%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 18 | Mar 27 | Mar 31 | Apr 5 | Apr 7 | Apr 11 | Apr 16 | Apr 21 | Apr 27 |
| 32°F | Feb 27 | Mar 4 | Mar 10 | Mar 14 | Mar 18 | Mar 25 | Mar 31 | Apr 5 | Apr 12 |
| 28°F | Jan 31 | Feb 9 | Feb 16 | Feb 22 | Feb 27 | Mar 2 | Mar 6 | Mar 12 | Mar 24 |
| 24°F | Jan 5 | Jan 17 | Jan 25 | Jan 31 | Feb 3 | Feb 8 | Feb 15 | Feb 23 | Mar 3 |
| 20°F84% of yrs | Dec 14 | Dec 25 | Jan 1 | Jan 6 | Jan 11 | Jan 18 | Jan 26 | Feb 3 | Feb 13 |
| 16°F37% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 20 | Oct 25 | Oct 29 | Nov 1 | Nov 3 | Nov 5 | Nov 9 | Nov 13 | Nov 19 |
| 32°F | Oct 27 | Nov 1 | Nov 5 | Nov 10 | Nov 13 | Nov 16 | Nov 20 | Nov 24 | Nov 30 |
| 28°F | Nov 5 | Nov 12 | Nov 18 | Nov 21 | Nov 25 | Nov 29 | Dec 2 | Dec 5 | Dec 9 |
| 24°F | Nov 15 | Nov 25 | Nov 30 | Dec 3 | Dec 6 | Dec 8 | Dec 12 | Dec 18 | Dec 23 |
| 20°F84% of yrs | Nov 28 | Dec 4 | Dec 9 | Dec 15 | Dec 18 | Dec 22 | Dec 27 | Jan 3 | Jan 12 |
| 16°F37% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Douglas, AZ, 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 85607 →Compare Douglas with another place →
Weather by month in Douglas
July is the warmest month at Douglas, AZ, averaging 95°F by day and 66°F at night; December is the coldest at 65°F and 30°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 82% of years and April still brings one in 29% of years.
Warmth for growing adds up to 5,618 growing degree days a year (base 50°F), fewer than at 52% of the 102 Arizona stations. 40% of them (2,275) have built up by the end of June, and July adds the most, 953.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 65 | 31 | 100% | 19 | 39 |
| Feb | 69 | 35 | 96% | 11 | 93 |
| Mar | 73 | 40 | 82% | 5 | 213 |
| Apr | 81 | 45 | 29% | 1 | 394 |
| May | 89 | 53 | 0% | 0 | 654 |
| Jun | 97 | 62 | 0% | 0 | 882 |
| Jul | 95 | 66 | 0% | 0 | 953 |
| Aug | 93 | 65 | 0% | 0 | 901 |
| Sep | 90 | 60 | 0% | 0 | 754 |
| Oct | 83 | 49 | 18% | <1 | 496 |
| Nov | 74 | 38 | 89% | 7 | 197 |
| Dec | 65 | 30 | 100% | 17 | 41 |
Monthly normals 1991–2020 at Douglas, AZ (4,040 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, Bisbee 1WNW, AZ, 23 miles west of Douglas and 1,520 feet higher, has a last frost 14 days later (April 1), a first frost 3 days earlier (November 10), a season 13 days shorter.
When it snows in Douglas, Arizona
Measurable snow is rare here: only 5 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Mc Neal, AZ, 16.7 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85607
| When | What to do |
|---|---|
| January 7 – January 21 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 21 – February 4 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 18 – March 4 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 18 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 13 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 85607 is 3 miles from Douglas, AZ, which stands at 4,040 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 85607 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.