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 99354
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 99354 in zone 7b (the coldest night of a typical year: 5 to 10°F).
The nearest station, Richland, WA, is 2 miles from the ZIP's center: its last spring frost comes after April 6 in half of years and after April 24 in one year in ten. By the USDA's method its plant hardiness zone is 7b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Richland, WA | 2 mi | 373 ft | April 6 | April 24 | October 24 | 7b |
| Eltopia (8 mi WSW), WA | 8 mi | 700 ft | April 21 | May 6 | October 22 | 7b |
| Pasco, WAPasco Tri Cities Airport | 10 mi | 407 ft | April 27 | May 10 | October 11 | 7a |
| Sagemoor, WA | 12 mi | 595 ft | April 30 | May 16 | October 13 | – |
| Kennewick, WA | 12 mi | 390 ft | March 28 | April 10 | October 30 | 8a |
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 Richland
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 8 | April 30 | April 25 | April 11 | October 14 | September 30 |
| 32°F | April 24 | April 13 | April 6 | March 22 | October 24 | October 10 |
| 28°F (hard freeze) | April 5 | March 27 | March 18 | March 1 | November 4 | October 20 |
| 24°F | March 18 | March 7 | February 28 | February 8 | November 16 | October 29 |
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.