Hillsboro climate
Hillsboro (Oregon, United States) has a warm-summer Mediterranean climate (Köppen Csb). The average temperature over the year is 11 °C52 °F, and about 1,495 mm59 in of precipitation falls in an average year.
Temperature by month
Precipitation by month
Hillsboro climate table
| Month | High °C°F | Low °C°F | Mean °C°F | Precip. mmin | Frost days |
|---|---|---|---|---|---|
| Jan | 846 | 236 | 541 | 2238.8 | 10 |
| Feb | 948 | 235 | 542 | 1465.7 | 10 |
| Mar | 1152 | 338 | 745 | 1797.0 | 5 |
| Apr | 1457 | 541 | 949 | 1174.6 | 1 |
| May | 1864 | 846 | 1355 | 732.9 | 0 |
| Jun | 2169 | 1050 | 1560 | 491.9 | 0 |
| Jul | 2577 | 1253 | 1865 | 120.5 | 0 |
| Aug | 2679 | 1254 | 1966 | 190.8 | 0 |
| Sep | 2373 | 1050 | 1662 | 582.3 | 0 |
| Oct | 1662 | 745 | 1253 | 1395.5 | 1 |
| Nov | 1151 | 439 | 745 | 2258.9 | 5 |
| Dec | 745 | 235 | 540 | 25610 | 11 |
| Year | 2679 | 235 | 1152 | 1,49559 | 44 |
“Year” row: highest monthly high, lowest monthly low, annual mean and annual total. Frost days are for the whole grid cell.
| Month | Humid. | Cloud | Solar | Daylight |
|---|---|---|---|---|
| Jan | 94% | 79% | 1.2 | 9:04 |
| Feb | 91% | 75% | 2.1 | 10:19 |
| Mar | 89% | 78% | 3.0 | 11:47 |
| Apr | 86% | 75% | 4.3 | 13:28 |
| May | 83% | 68% | 5.4 | 14:53 |
| Jun | 81% | 62% | 6.0 | 15:40 |
| Jul | 76% | 39% | 6.8 | 15:21 |
| Aug | 74% | 40% | 5.8 | 14:06 |
| Sep | 76% | 47% | 4.3 | 12:28 |
| Oct | 84% | 63% | 2.6 | 10:50 |
| Nov | 91% | 77% | 1.4 | 9:25 |
| Dec | 94% | 81% | 1.0 | 8:43 |
Humid. = average relative humidity at 2 m; cloud = average cloud amount; solar = average daily solar energy reaching the ground in kWh/m² (all-sky); daylight in hours:minutes, calculated for the 15th of each month.
What the climate of Hillsboro is like
The warmest month is August, with an average high of 26 °C79 °F and a low of 12 °C54 °F. The coldest is December, when highs average 7 °C45 °F and lows 2 °C35 °F. There is a clear seasonal cycle, with 14.4 °C25.9 °F between the average temperature of the warmest and the coolest month.
It is wet, with about 1,495 mm59 in of precipitation per year. The wettest three-month stretch is November–January, which brings 47% of the annual total. Months with less than 20 mm0.8 in on average: July and August. The wettest month is December (256 mm10 in), the driest is July (12 mm0.5 in).
Relative humidity ranges from 74% in August to 94% in December. The clearest skies (lowest average cloud amount, 39%) are typical of July. Average wind speed near the ground ranges from 2 km/h (1 mph) in May to 2 km/h (1 mph) in January. Daylight lasts from about 8.7 hours in December to 15.7 hours in June.
Best time to visit Hillsboro
Based on these averages, the most comfortable months for sightseeing and outdoor activities are June–September: average highs of 21 °C69 °F to 26 °C79 °F with 12 mm0.5 in to 58 mm2.3 in of precipitation per month.
The most challenging month is December, which is cold, with average highs of 7 °C45 °F and very wet (256 mm10 in).
Comfort score: months are ranked by how close they come to an average high of 21–28 °C (70–82 °F), lows above 5 °C (41 °F), little precipitation and moderate humidity. The best-ranked months of each place are recommended, even where none meets all of these. These are general rules of thumb applied to long-term averages.
What to pack for Hillsboro
- Winter (December–February) — highs 745 to 9 °C48 °F, lows around 2 °C35 °F, about 208 mm8.2 in of precipitation a month. Pack a warm coat, layers and closed shoes and a good rain jacket or umbrella and quick-drying shoes.
- Spring (March–May) — highs 1152 to 18 °C64 °F, lows 338 to 8 °C46 °F, about 123 mm4.8 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket and an umbrella or light rain jacket.
- Summer (June–August) — highs 2169 to 26 °C79 °F, lows 1050 to 12 °C54 °F, about 27 mm1.1 in of precipitation a month. Pack light layers — T-shirts plus a light sweater or jacket and an extra layer for the cooler mornings and evenings.
- Autumn (September–November) — highs 1151 to 23 °C73 °F, lows 439 to 10 °C50 °F, about 140 mm5.5 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket and an umbrella or light rain jacket.
How Hillsboro compares
Compared with Portland, about 24 km to the east, Hillsboro is on average 0.9 °C1.7 °F cooler and receives a similar amount of precipitation. The difference is largest in August (2.4 °C4.3 °F cooler).
Of the 222 places in the United States covered by World Climates, Hillsboro is the 177th warmest by annual mean temperature and the 6th wettest by annual precipitation. See all of them on the United States climate page.
Places in other countries with the most similar temperature and rainfall pattern: Vancouver (Canada, Csb), Surrey (Canada, Csb) and Victoria (Canada, Csb).
Nearby places
- Portland 24 km · 12 °C54 °F · 1,484 mm58 in
- Salem 65 km · 11 °C53 °F · 1,370 mm54 in
- Eugene 164 km · 12 °C53 °F · 1,375 mm54 in
- Seattle 237 km · 11 °C52 °F · 1,232 mm49 in
- Everett 280 km · 11 °C52 °F · 1,253 mm49 in
- Tri-Cities 304 km · 14 °C57 °F · 278 mm11 in
- Victoria 325 km · 11 °C51 °F · 991 mm39 in
- Abbotsford 397 km · 10 °C50 °F · 1,403 mm55 in
Frequently asked questions
What is the warmest month in Hillsboro?
August is the warmest month in Hillsboro, with an average high of 26 °C (79 °F) and an average low of 12 °C (54 °F).
What is the coldest month in Hillsboro?
December is the coldest month, with an average high of 7 °C (45 °F) and an average low of 2 °C (35 °F).
When does it rain the most in Hillsboro?
December is the wettest month with about 256 mm (10.1 in) of precipitation; July is the driest with about 12 mm (0.5 in).
What is the best time to visit Hillsboro?
Judging by long-term averages, the most comfortable months are June–September.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.
The grid cell’s average elevation is 226 m, while Hillsboro lies at about 59 m. Temperatures on this page were therefore adjusted by +1.1 °C2 °F using the standard lapse rate of 6.5 °C per 1,000 m.