Last spring frost
Apr 16
Frost Dates for Rio Rico, AZ
First fall frost
Nov 2
Growing season
199 days
Hardiness zone
8b
In an average year around Rio Rico, AZ, the last spring frost (32°F) is about Apr 16 and the first fall frost is about Nov 2, giving roughly a 199-day growing season. To be safe most years, wait until Mar 28 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | May 18 | May 2 | Apr 18 |
| Freeze (32°F) | May 4 | Apr 16 | Mar 28 |
| Hard (28°F) | Apr 15 | Mar 22 | Feb 26 |
| Severe (24°F) | Mar 23 | Feb 27 | Jan 31 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 18 | May 13 | May 9 | May 5 | May 2 | Apr 30 | Apr 27 | Apr 22 | Apr 18 |
| 32°F | May 4 | Apr 29 | Apr 24 | Apr 20 | Apr 16 | Apr 12 | Apr 8 | Apr 3 | Mar 28 |
| 28°F | Apr 15 | Apr 8 | Apr 3 | Mar 28 | Mar 22 | Mar 16 | Mar 10 | Mar 4 | Feb 26 |
| 24°F | Mar 23 | Mar 12 | Mar 6 | Mar 2 | Feb 27 | Feb 22 | Feb 17 | Feb 10 | Jan 31 |
| 20°F | Mar 1 | Feb 23 | Feb 16 | Feb 10 | Feb 3 | Jan 30 | Jan 21 | Jan 10 | Dec 29 |
| 16°F | Feb 17 | Feb 5 | Jan 31 | Jan 24 | Jan 16 | Jan 8 | Dec 31 | Dec 23 | Dec 13 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Oct 10 | Oct 24 | Nov 6 |
| Freeze (32°F) | Oct 19 | Nov 2 | Nov 16 |
| Hard (28°F) | Oct 29 | Nov 14 | Nov 29 |
| Severe (24°F) | Nov 8 | Nov 25 | Dec 12 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 10 | Oct 15 | Oct 19 | Oct 21 | Oct 24 | Oct 27 | Oct 30 | Nov 2 | Nov 6 |
| 32°F | Oct 19 | Oct 25 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 16 |
| 28°F | Oct 29 | Nov 2 | Nov 7 | Nov 10 | Nov 14 | Nov 17 | Nov 20 | Nov 23 | Nov 29 |
| 24°F | Nov 8 | Nov 15 | Nov 19 | Nov 22 | Nov 25 | Nov 29 | Dec 2 | Dec 5 | Dec 12 |
| 20°F | Nov 22 | Nov 27 | Dec 1 | Dec 6 | Dec 10 | Dec 14 | Dec 19 | Dec 27 | Jan 9 |
| 16°F | Dec 4 | Dec 10 | Dec 15 | Dec 21 | Dec 27 | Jan 1 | Jan 9 | Jan 24 | Feb 1 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Nogales 6 N, Az, about 3.4 miles away@if(!empty($station['elevation_ft'])), at 3,461 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Rio Rico, AZ?
On average, the last spring frost (32°F) around Rio Rico, AZ is about Apr 16. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 28.
When is the first frost in the fall?
The first fall frost around Rio Rico, AZ typically arrives about Nov 2. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Apr 16 on average, or Mar 28 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 199 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 85648 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026