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Will it freeze in Prosser in the next 7 nights?
No overnight lows at or below 32°F are forecast in Prosser during the next 7 nights in the available NWS frost forecast.
Tonight: forecast low 34°F. Frost possible.
NWS forecast period: Thu, Nov 5, 6:00 PM PST to Fri, Nov 6, 6:00 AM PST.
3 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 34°F Frost possible · Areas Of Fog
- Fri, Nov 6 37°F Above 36°F · Slight Chance Rain Showers then Areas Of Fog
- Sat, Nov 7 41°F Above 36°F · Mostly Cloudy
- Sun, Nov 8 35°F Frost possible · Mostly Cloudy
- Mon, Nov 9 36°F Frost possible · Chance Rain Showers
- Tue, Nov 10 40°F Above 36°F · Chance Rain Showers
- Wed, Nov 11 40°F Above 36°F · Mostly Cloudy
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in Prosser
The median first fall hard-freeze date (28°F) is November 2, from NOAA’s 1991–2020 Climate Normals at Prosser. This is the 50% probability date, not a forecast for this year.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | Apr 16 · May 2 · May 24 | Sep 26 · Oct 9 · Oct 25 | 158 days |
| 32°F freeze | Mar 24 · Apr 14 · May 7 | Oct 5 · Oct 22 · Nov 7 | 189 days |
| 28°F hard freeze | Mar 2 · Mar 23 · Apr 22 | Oct 18 · Nov 2 · Nov 20 | 224 days |
Average high temperature by month
1991–2020 normals at Prosser
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for Prosser, WA come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Prosser (station USC00456768, elevation 830 ft), 0.7 mi from Prosser. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near Prosser
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Grandview, WA | 7.5 mi | May 1 | Oct 6 |
| Sunnyside, WA | 14 mi | May 1 | Oct 6 |
| West Richland, WA | 19 mi | Apr 6 | Oct 24 |
| Richland, WA | 23 mi | Apr 6 | Oct 24 |
| Kennewick, WA | 29 mi | Mar 28 | Oct 30 |
| Toppenish, WA | 29 mi | Apr 21 | Oct 15 |
| Umatilla, OR | 29 mi | Mar 30 | Nov 4 |
| Pasco, WA | 31 mi | Apr 27 | Oct 11 |
| Hermiston, OR | 35 mi | Apr 26 | Oct 10 |
| Union Gap, WA | 42 mi | May 8 | Oct 4 |
Frequently asked questions
When is the last frost in Prosser?
On average, the last spring frost (32°F) in Prosser is around April 14. In about 1 year in 10 it comes after May 7, and in 9 years in 10 it comes after March 24.
When is the first frost in Prosser?
The first fall frost (32°F) usually arrives around October 22. There’s a 10% chance of a freeze by October 5 and a 90% chance by November 7.
Can it frost in Prosser after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after May 2.
What growing zone is Prosser?
Prosser is in USDA Plant Hardiness Zone 7b (average annual extreme minimum temperature 5 to 10°F), based on the 2023 USDA map for ZIP code 99350. See growing zones in Washington.
More: all Washington frost dates · Washington growing zones · frost vs. freeze