USDA Hardiness Zone 9b
Frost Dates for 85120 — Apache Junction, Arizona
NOAA 1991–2020 normals from E Mesa, AZ (1,518 ft), 5 miles west.
Updated
In Apache Junction, the last spring frost (32°F) is around February 1 in half of years and has passed by February 28 in nine years out of ten. The first fall frost comes around December 10, as early as November 22 one year in ten, leaving a typical freeze-free season of 312 days (NOAA, E Mesa, AZ).
- Last spring frost
- February 1
- First fall frost
- December 10
- Growing season
- 312 days
- Hardiness zone
- 9b
50% probability
50% probability
freeze-free, 50%
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 0%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
0 of 24 observed
NOAA normal
Frost risk by date in Apache Junction
Half of springs at E Mesa, AZ see their last 32°F night by February 1; only one in ten is past it by January 1, and one in ten still has one after February 28. Planting tender crops after February 12 leaves a 30% risk of a frost on them, after February 19 20%, and after February 28 10%. The 27 days between the even-odds date and the one-in-ten date is wider than at 71% 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 December 10 in half of years, as early as November 22 one year in ten, and holds off past January 1 one year in ten. A hard freeze of 28°F follows 16 days later, around December 26; in spring the one-in-ten date for 28°F is February 11, 17 days before the 32°F one. The freeze-free season lasts 312 days in a typical year, longer than at 78% of the 98 Arizona stations; it reaches 348 days one year in ten and falls short of 280 one year in ten. On average 11 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 26 days longer, to about February 27, and return around November 30. A 24°F night is unusual: 15% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 31 | Feb 8 | Feb 15 | Feb 20 | Feb 27 | Mar 1 | Mar 5 | Mar 10 | Mar 15 |
| 32°F98% of yrs | Jan 1 | Jan 10 | Jan 18 | Jan 26 | Feb 1 | Feb 6 | Feb 12 | Feb 19 | Feb 28 |
| 28°F70% of yrs | Dec 13 | Dec 23 | Dec 31 | Jan 4 | Jan 11 | Jan 17 | Jan 26 | Feb 2 | Feb 11 |
| 24°F15% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 13 | Nov 18 | Nov 22 | Nov 26 | Nov 30 | Dec 2 | Dec 6 | Dec 10 | Dec 15 |
| 32°F98% of yrs | Nov 22 | Nov 28 | Dec 2 | Dec 6 | Dec 10 | Dec 14 | Dec 19 | Dec 24 | Jan 1 |
| 28°F70% of yrs | Dec 1 | Dec 9 | Dec 13 | Dec 19 | Dec 26 | Jan 1 | Jan 5 | Jan 14 | Jan 28 |
| 24°F15% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at E Mesa, 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 85120 →Compare Apache Junction with another place →
Weather by month in Apache Junction
July is the warmest month at E Mesa, AZ, averaging 106°F by day and 79°F at night; December is the coldest at 66°F and 40°F. From March to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 47% of years.
Warmth for growing adds up to 8,239 growing degree days a year (base 50°F), more than at 81% of the 102 Arizona stations. 40% of them (3,309) have built up by the end of June, and July adds the most, 1,314. Precipitation totals 11.0 inches a year, most in February (1.5") and least in June (0.1"); May to September bring 35% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 68 | 41 | 1.4 | 79% | 3 | 161 |
| Feb | 70 | 43 | 1.5 | 47% | 3 | 195 |
| Mar | 77 | 48 | 1.3 | 8% | <1 | 386 |
| Apr | 85 | 53 | 0.4 | 0% | 0 | 578 |
| May | 94 | 62 | 0.2 | 0% | 0 | 868 |
| Jun | 104 | 71 | 0.1 | 0% | 0 | 1122 |
| Jul | 106 | 79 | 1.2 | 0% | 0 | 1314 |
| Aug | 105 | 78 | 1.3 | 0% | 0 | 1286 |
| Sep | 100 | 71 | 1.1 | 0% | 0 | 1074 |
| Oct | 90 | 59 | 0.6 | 0% | 0 | 753 |
| Nov | 77 | 48 | 0.8 | 24% | 1 | 370 |
| Dec | 66 | 40 | 1.1 | 83% | 5 | 132 |
Monthly normals 1991–2020 at E Mesa, AZ (1,518 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, Apache Junction 5 NE, AZ, 6 miles northeast of Apache Junction and 552 feet higher, has a last frost 10 days later (February 11), the same first-frost date, a season 8 days shorter.
When it snows in Apache Junction, Arizona
Measurable snow is rare here: only 0 of 24 winters from 1991 to 2020 recorded 0.1 inch or more at Apache Junction 5 NE, AZ, 6.3 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 85120
| When | What to do |
|---|---|
| November 23 – December 7 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| December 7 – December 21 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| January 4 – January 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| February 1 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 10 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 85120 is 5 miles from E Mesa, AZ, which stands at 1,518 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 10 other ZIP codes share the station; its figures are presented in full for 85212 (Mesa). The 2023 USDA Plant Hardiness Zone Map lists ZIP 85120 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°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.