USDA Hardiness Zone 9b
Frost Dates for 85263 — Rio Verde, Arizona
NOAA 1991–2020 normals from Fountain Hills, AZ (1,580 ft), 9 miles south.
Updated
A freeze (32°F) reaches Rio Verde in 63% of winters. When it does, the first fall frost comes around December 28 and the last spring frost around January 6; after February 11 the chance of another is under 6%.
- Last spring frost
- January 6
- First fall frost
- December 28
- Winters with a freeze
- 63%
- Hardiness zone
- 9b
50%, in freezing years
50%, in freezing years
32°F or below, 1991–2020
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 23 observed
NOAA normal
Frost risk by date in Rio Verde
In the 63% of winters that bring a 32°F night, half of springs at Fountain Hills, AZ see their last 32°F night by January 6; only one in ten is past it by December 14, and one in ten still has one after February 11. Counting the winters with no freeze at all, the risk of a 32°F night after February 11 is under 6% and after January 6 32%. The 36 days between the even-odds date and the one-in-ten date is wider than at 95% 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 28 in half of years, as early as December 4 one year in ten, and holds off past January 27 one year in ten. A hard freeze of 28°F is less common: it came in 14% of winters. The freeze-free season lasts 356 days in a typical year, longer than at 98% of the 98 Arizona stations; it reaches 365 days one year in ten and falls short of 324 one year in ten. On average 4 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 January 31, and return around December 14. A 24°F night is unusual: 1% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F98% of yrs | Dec 31 | Jan 7 | Jan 16 | Jan 23 | Jan 31 | Feb 5 | Feb 14 | Feb 20 | Mar 1 |
| 32°F63% of yrs | Dec 14 | Dec 23 | Dec 30 | Jan 2 | Jan 6 | Jan 12 | Jan 21 | Jan 30 | Feb 11 |
| 28°F14% of yrs | too rare for a date | ||||||||
| 24°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F98% of yrs | Nov 25 | Dec 1 | Dec 6 | Dec 11 | Dec 14 | Dec 18 | Dec 22 | Dec 27 | Jan 3 |
| 32°F63% of yrs | Dec 4 | Dec 13 | Dec 18 | Dec 23 | Dec 28 | Dec 31 | Jan 4 | Jan 13 | Jan 27 |
| 28°F14% of yrs | too rare for a date | ||||||||
| 24°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Fountain Hills, 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 85263 →Compare Rio Verde with another place →
Weather by month in Rio Verde
July is the warmest month at Fountain Hills, AZ, averaging 103°F by day and 80°F at night; December is the coldest at 63°F and 44°F. From March to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 11% of years.
Warmth for growing adds up to 8,179 growing degree days a year (base 50°F), more than at 80% of the 102 Arizona stations. 40% of them (3,280) have built up by the end of June, and July adds the most, 1,291. Precipitation totals 10.0 inches a year, most in January (1.4") and least in June (0.1"); May to September bring 32% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 64 | 45 | 1.4 | 34% | 1 | 154 |
| Feb | 67 | 46 | 1.3 | 11% | <1 | 204 |
| Mar | 74 | 51 | 1.3 | 0% | 0 | 384 |
| Apr | 82 | 56 | 0.3 | 0% | 0 | 576 |
| May | 91 | 65 | 0.2 | 0% | 0 | 860 |
| Jun | 101 | 73 | 0.1 | 0% | 0 | 1101 |
| Jul | 103 | 80 | 0.8 | 0% | 0 | 1291 |
| Aug | 102 | 80 | 1.3 | 0% | 0 | 1266 |
| Sep | 97 | 74 | 0.8 | 0% | 0 | 1062 |
| Oct | 87 | 63 | 0.6 | 0% | 0 | 763 |
| Nov | 74 | 51 | 0.7 | 4% | <1 | 379 |
| Dec | 63 | 44 | 1.2 | 37% | 2 | 138 |
Monthly normals 1991–2020 at Fountain Hills, AZ (1,580 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, Pinnacle Peak, AZ, 10 miles west of Rio Verde and 985 feet higher, has a last frost 21 days later (January 27), a first frost 7 days earlier (December 21), a season 26 days shorter.
When it snows in Rio Verde, Arizona
Measurable snow is rare here: only 0 of 23 winters from 1991 to 2020 recorded 0.1 inch or more at Fountain Hills, AZ, 8.5 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 85263 is 9 miles from Fountain Hills, AZ, which stands at 1,580 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 85268 (Fountain Hills). The 2023 USDA Plant Hardiness Zone Map lists ZIP 85263 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.