Ontario, OR climate
Ontario has chilly winters and hot summers, with very little rain. A typical July afternoon reaches 93°, a January night drops to 23°, and about 15 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Ontario feels like
Winter
Spring
Summer
Fall
Ontario weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 38° | 23° | 1.3" | 6.1" | 11 | 16° – 36° |
| February | 46° | 27° | 0.9" | 2.3" | 8 | 26° – 44° |
| March | 58° | 33° | 1.0" | 0.5" | 11 | 40° – 49° |
| April | 65° | 37° | 0.9" | 0 | 9 | 46° – 56° |
| May | 75° | 46° | 1.3" | 0 | 8 | 54° – 66° |
| June | 83° | 53° | 0.8" | 0 | 6 | 63° – 76° |
| July | 93° | 59° | 0.2" | 0 | 2 | 66° – 82° |
| August | 92° | 57° | 0.1" | 0 | 3 | 68° – 77° |
| September | 81° | 47° | 0.4" | 0 | 3 | 60° – 68° |
| October | 66° | 37° | 0.7" | 0 | 7 | 44° – 57° |
| November | 49° | 28° | 1.0" | 1.1" | 10 | 31° – 44° |
| December | 38° | 23° | 1.5" | 5.4" | 11 | 21° – 37° |
| Year | 65° | 39° | 10.1" | 15.4" | 91 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Ontario
Ontario gets 10 inches of rain and melted snow a year. December is the wettest month and August the driest. Rain or snow falls on about 91 days a year.
About 168 frost-free days a year
In half of years the last 32° night comes by April 22 and the first one by October 9. That leaves about 168 frost-free days for gardens, shorter than 63% of U.S. towns.
Heating and cooling a home in Ontario
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Ontario, 86% of that work is heating and 14% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
How Ontario compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Ontario averaged 1.4° warmer than the 1900s. The biggest change is in January (+3.4°). The shift is larger than in 62% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Ontario’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. January swings the most: between 1991 and 2020 its average temperature ranged from 16° to 36°. September is the most reliable, staying within 8°.
Common questions about Ontario’s climate
What is the coldest month in Ontario?
January, with a typical high of 38° and a low of 23°.
What is the hottest month in Ontario?
July, with a typical high of 93° and a low of 59°. About 62 days a year reach 90°.
How much snow does Ontario get?
About 15 inches in a normal winter, most of it in January.
When is the first frost in Ontario?
In half of years the first 32° night comes by October 9, and the last spring frost by April 22.
What is the rainiest month in Ontario?
December, with 1.5 inches of rain and melted snow. The year totals 10 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Ontario itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Malheur Branch Exp Stn, OR (4 mi, snow) and Ontario Ksrv, OR (1 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.