Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 85640
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 85640 in zone 8b (the coldest night of a typical year: 15 to 20°F).
The nearest station, Tumacacori National Monument, AZ, is 0 miles from the ZIP's center: its last spring frost comes after April 5 in half of years and after April 25 in one year in ten. By the USDA's method its plant hardiness zone is 8b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Tumacacori National Monument, AZ | 0 mi | 3,267 ft | April 5 | April 25 | November 10 | 8b |
| Rio Rico, AZNogales (6 mi N) | 9 mi | 3,461 ft | April 16 | May 4 | November 2 | – |
| Nogales, AZNogales International Airport | 16 mi | 3,932 ft | March 20 | April 13 | November 17 | 8b |
| Santa Rita Experiment Range, AZ | 18 mi | 4,300 ft | February 25 | March 29 | December 5 | – |
| Green Valley, AZ | 23 mi | 2,900 ft | February 25 | March 18 | November 27 | 9a |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at Tumacacori National Monument
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | May 9 | April 30 | April 23 | April 6 | October 30 | October 13 |
| 32°F | April 25 | April 13 | April 5 | March 13 | November 10 | October 21 |
| 28°F (hard freeze) | April 8 | March 25 | March 12 | February 16 | November 20 | November 1 |
| 24°F | March 11 | February 28 | February 16 | January 15 | December 2 | November 10 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.