Photo: Quintin Soloviev · CC BY 4.0Few U.S. towns get less rain and snow than Prosser: 8 inches a year
In January the night’s low is typically 28°. Only 63° separates winter nights from summer afternoons. Its July heat outdoes that of 78% of U.S. towns. Seedlings are safe outdoors from about April 14, with the first autumn frost due around October 22.
A year in Prosser at a glance
Each month’s typical high and low, and what it brings.
What stands out about Prosser’s climate
Compared with towns across the U.S., with Prosser’s place in Washington beside it.
What a year in Prosser feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 189 frost-free days a year
In half of years the last 32° night comes by April 14 and the first by October 22. Frost and day counts come from NOAA’s station at Prosser, WA, 0.7 miles from the town’s center, 120 ft higher.
The 2023 USDA map puts Prosser’s center in zone 7b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 6°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 8 inches of rain a year
December is the wettest month and August the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Prosser
86% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Prosser, WA.
Living with Prosser’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
189 frost-free days in zone 7b. The last frost comes by Apr 14 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 22.
Months with highs of 62–84° and lows of 40° or more: May, June and September. 1.6 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Prosser from natural hazards, river flooding is the largest share (65%); heat waves, cold waves, winter storms and ice storms together are 10%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Prosser and similar climates
TownRatings has no climate map of the towns around Prosser yet.
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Prosser averaged 0.9° warmer than the 1900s. The biggest change is in January (+3.0°).
A smaller shift than in 85% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Prosser compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Prosser’s place among Washington’s.
Prosser weather by month
Highs, lows and precipitation from NOAA’s grid at Prosser’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 40° | 28° | 1.1" | 21° – 40° |
| February | 47° | 29° | 0.8" | 25° – 44° |
| March | 56° | 34° | 0.6" | 35° – 50° |
| April | 65° | 40° | 0.6" | 47° – 58° |
| May | 74° | 47° | 0.7" | 56° – 65° |
| June | 81° | 53° | 0.5" | 63° – 75° |
| July | 90° | 59° | 0.2" | 66° – 79° |
| August | 89° | 57° | 0.2" | 68° – 75° |
| September | 79° | 49° | 0.3" | 61° – 68° |
| October | 64° | 39° | 0.7" | 47° – 57° |
| November | 49° | 32° | 0.9" | 35° – 46° |
| December | 39° | 27° | 1.2" | 26° – 38° |
| Year | 64° | 41° | 7.8" |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 25° to 44°. September is the most reliable, staying within 7°.
Where Prosser’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Prosser’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Prosser, WA, 0.7 miles from the town’s center, 120 ft higher; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Prosser’s climate
What is the weather like in Prosser?
A typical July afternoon reaches 90°, a January night drops to 28°. Milder January nights than 69% of U.S. towns; hotter July afternoons than 78% of U.S. towns.
How cold does it get in Prosser in winter?
December nights average 27°. About 109 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 26°.
How hot does it get in Prosser?
July, with a typical high of 90° and a low of 59°. About 47 days a year reach 90° and 7 reach 100° (Prosser, WA).
When is the first and last frost in Prosser?
In half of years the last spring frost (32°) comes by April 14 and the first fall frost by October 22, about 189 frost-free days, at Prosser, WA.
What growing zone is Prosser in?
Zone 7b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 6°.
What is the best time of year to visit Prosser?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Prosser getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 85% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Prosser.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.