Climateby Month

Hillsboro, OR climate by month

NOAA 1991-2020 normals · 195 ft elevation

Hillsboro has warm summers and chilly winters. Highs peak at 82°F in August and fall to 44°F in December. The wettest month is December (about 21 wet days) and the driest is July (about 3). Normal snowfall is about 5.2 in a year. By our comfort score the best month is June.

Warmest month
82°F
August normal high
Coldest month
33°F
January normal low
Wet days a year
152
44.1 in of precipitation
Snow a year
5.2 in
normal snowfall

How warm is Hillsboro?

Normal highs range from 44°F in December to 82°F in August.

30°40°50°60°70°80°90° January: normal high 45°F (7°C), low 33°F (1°C) February: normal high 49°F (9°C), low 33°F (1°C) March: normal high 55°F (13°C), low 36°F (2°C) April: normal high 60°F (16°C), low 39°F (4°C) May: normal high 68°F (20°C), low 45°F (7°C) June: normal high 73°F (23°C), low 50°F (10°C) July: normal high 81°F (27°C), low 54°F (12°C) August: normal high 82°F (28°C), low 54°F (12°C) 82° 54° September: normal high 76°F (24°C), low 49°F (9°C) October: normal high 63°F (17°C), low 42°F (6°C) November: normal high 51°F (11°C), low 36°F (2°C) December: normal high 44°F (7°C), low 33°F (1°C) 44° 33° JFMAMJJASOND

Bars run from the normal low to the normal high for each month.

How rainy is Hillsboro?

December has the most wet days (about 21); the year brings about 44 in of precipitation.

January: 20 wet days February: 15 wet days March: 18 wet days April: 16 wet days May: 12 wet days June: 8 wet days July: 3 wet days 3 August: 3 wet days September: 6 wet days October: 12 wet days November: 19 wet days December: 21 wet days 21 JFMAMJJASOND

Wet day: at least 0.01 in of rain or melted snow, counted from daily records 1991-2020.

How much does it snow?

Normal snowfall is 5.2 in a year, most of it in December.

January: 1.6 in of snow February: 1.6 in of snow March: 0.0 in of snow 0.0 April: 0.0 in of snow May: 0.0 in of snow June: 0.0 in of snow July: 0.0 in of snow August: 0.0 in of snow September: 0.0 in of snow October: 0.0 in of snow November: 0.3 in of snow December: 1.7 in of snow 1.7 JFMAMJJASOND

How humid is Hillsboro?

Muggy days (dew point 65°F or higher) are rare in any month.

January: 0 muggy days 0 February: 0 muggy days March: 0 muggy days April: 0 muggy days May: 0 muggy days June: 0 muggy days July: 0 muggy days 0 August: 0 muggy days September: 0 muggy days October: 0 muggy days November: 0 muggy days December: 0 muggy days JFMAMJJASOND

Muggy day: daily mean dew point of 65°F or higher, from hourly observations 1991-2020 at Portland International Airport, 19 mi ENE of the city center (the nearest airport with complete hourly records).

How much daylight?

Daylight ranges from about 8.8 hours in December to 15.6 hours in June.

January: 9.2 hours of daylight February: 10.4 hours of daylight March: 11.9 hours of daylight April: 13.5 hours of daylight May: 14.9 hours of daylight June: 15.6 hours of daylight 15.6 July: 15.3 hours of daylight August: 14.1 hours of daylight September: 12.5 hours of daylight October: 10.9 hours of daylight November: 9.5 hours of daylight December: 8.8 hours of daylight 8.8 JFMAMJJASOND
See all numbers
Monthly climate normals and day counts for Hillsboro, 1991-2020
MonthHighLowPrecip.Wet daysSnowMuggy daysDaylight
January 45°F33°F 7.2 in20 1.6 in 0 9.2 h
February 49°F33°F 4.9 in15 1.6 in 0 10.4 h
March 55°F36°F 4.8 in18 0.0 in 0 11.9 h
April 60°F39°F 3.3 in16 0.0 in 0 13.5 h
May 68°F45°F 2.1 in12 0.0 in 0 14.9 h
June 73°F50°F 1.2 in8 0.0 in 0 15.6 h
July 81°F54°F 0.3 in3 0.0 in 0 15.3 h
August 82°F54°F 0.5 in3 0.0 in 0 14.1 h
September 76°F49°F 1.3 in6 0.0 in 0 12.5 h
October 63°F42°F 3.6 in12 0.0 in 0 10.9 h
November 51°F36°F 6.7 in19 0.3 in 0 9.5 h
December 44°F33°F 8.2 in21 1.7 in 0 8.8 h

High and low: NOAA 1991-2020 normal daily high and low. Wet days: at least 0.01 in of rain or melted snow. Muggy days: daily mean dew point 65°F or higher.

Best months to visit Hillsboro

By our comfort score, the best month is June.

Comfort score by month (0-100) and its parts, in days per month
MonthScoreComfortableNotable rainHot or cold
Jan 310146
Feb 391102
Mar 494110
Apr 598100
May 731561
Jun 791842
Jul 701318
Aug 671218
Sep 701633
Oct 591380
Nov 361132
Dec 290147

Score = 40 × share of comfortable days + 25 × share of days without notable rain + 20 × share of days neither hot (90°F+) nor cold (high 40°F or below) + 15 × daylight. How the score works.

Frost dates in Hillsboro

The last spring frost typically comes around Apr 16, and the first fall frost around Oct 23, leaving 191 frost-free days in a typical year.

Frost and freeze dates for Hillsboro
Typical date1 year in 10
Last spring frost (32°F)Apr 16after May 3
First fall frost (32°F)Oct 23before Oct 3
Last hard freeze (28°F)Mar 13after Apr 9
First hard freeze (28°F)Nov 12before Oct 20
Frost-free season191 daysunder 161 days

"Typical" is the date with a 50% chance of a later spring frost (or earlier fall frost). Planting after the "1 year in 10" spring date gives a 90% chance of no further frost. The Old Farmer's Almanac publishes 30% dates, which fall between our typical and 1-in-10 dates.

Station: Portland-Hillsboro Airport (USW00094261), NOAA 1991-2020 freeze probabilities. Frost dates for every city in Oregon.

Hottest and coldest readings, 1991-2020

The highest reading was 108°F (July 28, 1998); the lowest was 7°F (February 3, 1996).

From the temperature station's daily records with NOAA quality flags removed. Not an all-time record.

Near Hillsboro

Similar climates elsewhere

Where the numbers come from

  • Temperature and snow depth: Forest Grove (USC00352997), 5.5 mi W of the city center, 180 ft . NOAA normals and daily records, 1991-2020.
  • Rain and snowfall: Dilley 2 S (USC00352325), 7.3 mi SW of the city center, 194 ft . NOAA normals and daily records, 1991-2020.
  • Frost dates and humidity and wind by hour: Portland-Hillsboro Airport (USW00094261), 2.3 mi ENE of the city center, 204 ft . NOAA normals and daily records, 1991-2020.
  • Daily humidity and wind: Portland International Airport (726980-24229), 19 mi ENE of the city center, 22 ft (173 ft lower than the city). Hourly observations, 1991-2020.
  • Not available for this location: cloud cover (no station close enough or similar enough in elevation).

Distances from the city center (USGS). Methodology · Report an error