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 99224
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 99224 in zone 6b (the coldest night of a typical year: -5 to 0°F).
The nearest station, Spokane, WA, is 2 miles from the ZIP's center: its last spring frost comes after April 26 in half of years and after May 10 in one year in ten. By the USDA's method its plant hardiness zone is 6b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Spokane, WASpokane International Airport | 2 mi | 2,353 ft | April 26 | May 10 | October 12 | 6b |
| Spokane Weather Office, WA | 5 mi | 2,392 ft | May 10 | May 30 | September 26 | – |
| Spokane Felts Field, WA | 10 mi | 1,953 ft | April 26 | May 10 | October 15 | 7a |
| Spokane (17 mi SSW), WA | 16 mi | 2,267 ft | May 30 | July 13 | September 4 | – |
| Deer Park, WADeer Park Airport | 23 mi | 2,191 ft | May 22 | June 15 | September 14 | 6a |
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 Spokane
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 26 | May 15 | May 8 | April 26 | October 1 | September 17 |
| 32°F | May 10 | May 2 | April 26 | April 9 | October 12 | September 29 |
| 28°F (hard freeze) | April 28 | April 15 | April 6 | March 15 | October 23 | October 7 |
| 24°F | April 4 | March 25 | March 13 | February 26 | November 3 | October 16 |
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.