Hillsboro, OR climate
Hillsboro has mild winters and pleasant summers. A typical July afternoon reaches 81°, a January night drops to 35°, and about 5 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Hillsboro feels like
Winter
Spring
Summer
Fall
Hillsboro 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 | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 47° | 35° | 5.8" | 1.6" | 20 | 2 | 35° – 46° |
| February | 51° | 36° | 4.2" | 1.6" | 15 | 1 | 37° – 49° |
| March | 56° | 38° | 4.1" | 0 | 18 | 0 | 44° – 52° |
| April | 61° | 41° | 2.9" | 0 | 16 | 0 | 46° – 56° |
| May | 68° | 46° | 2.1" | 0 | 12 | 0 | 52° – 61° |
| June | 73° | 50° | 1.4" | 0 | 8 | 0 | 58° – 68° |
| July | 81° | 54° | 0.4" | 0 | 3 | 0 | 62° – 71° |
| August | 82° | 54° | 0.5" | 0 | 3 | 0 | 65° – 71° |
| September | 76° | 50° | 1.3" | 0 | 6 | 0 | 59° – 66° |
| October | 64° | 44° | 3.3" | 0 | 12 | 0 | 49° – 58° |
| November | 53° | 39° | 5.8" | 0.3" | 19 | 0 | 40° – 51° |
| December | 46° | 35° | 6.8" | 1.7" | 21 | 1 | 36° – 44° |
| Year | 63° | 43° | 38.4" | 5.2" | 152 | 4 |
“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 Hillsboro
Hillsboro gets 38 inches of rain and melted snow a year. December is the wettest month and July the driest. Rain or snow falls on about 152 days a year.
About 191 frost-free days a year
In half of years the last 32° night comes by April 16 and the first one by October 23. That leaves about 191 frost-free days for gardens, longer than 65% of U.S. towns.
Heating and cooling a home in Hillsboro
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Hillsboro, 95% of that work is heating and 5% 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.
Hillsboro and its neighbors
Hillsboro borders 3 towns with climate data. January nights across them vary by 0.5°. Rockcreek has the coldest January nights (35°) and Beaverton the hottest July afternoons (81°). Hillsboro’s January low is 35° and its July high 81°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Hillsboro 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 Hillsboro averaged 1.2° warmer than the 1900s. The biggest change is in January (+3.0°). The shift is smaller than in 51% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Hillsboro’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 37° to 49°. September is the most reliable, staying within 7°.
Common questions about Hillsboro’s climate
What is the coldest month in Hillsboro?
December, with a typical high of 46° and a low of 35°.
What is the hottest month in Hillsboro?
August, with a typical high of 82° and a low of 54°. About 17 days a year reach 90°.
How much snow does Hillsboro get?
About 5 inches in a normal winter, most of it in December.
When is the first frost in Hillsboro?
In half of years the first 32° night comes by October 23, and the last spring frost by April 16.
What is the rainiest month in Hillsboro?
December, with 6.8 inches of rain and melted snow. The year totals 38 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Hillsboro itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Dilley 2 S, OR (10 mi, snow) and Portland-hillsboro Airport, 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.