Portland-hillsboro, OR Climate: Temperature & Rain by Month
Pulled from NOAA NCEI 1991–2020 normals →: climate measurements used in PlainClimate's documented score
30-year climate normals (1991-2020) from Portland-hillsboro's primary NOAA station, PORTLAND-HILLSBORO AP.
The climate verdict for Portland-hillsboro
A compact 27.4°F seasonal swing gives Portland-hillsboro, Oregon a steadier-than-extreme annual shape. NOAA reports an annual average of 53°F. Its climate comfort score of 68/100 (good) lands mid-pack nationally, exceeding 56% of station-mapped location scores.
- 53°F
- yearly average temperature, NOAA normal
- 68/100
- comfort score, above 56% of station-mapped location scores
- 35.9"
- precipitation, annual total
- 190 days
- frost-free days per growing season
Portland-hillsboro: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USW00094261 · Portland-hillsboro, OR 53°F mean · 35.9" precip
TEMP-COOL · RANK-MID · PHOTO-FINISH · PRCP-MID · SWING-NARROW · COMF-MID · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 53°F
- RANK-MID #3,499
- PHOTO-FINISH ≈ Idleyld Park
- PRCP-MID 35.9"
- SWING-NARROW 27°F
- COMF-MID 68/100
- LOAD-HEAT 4,830 HDD
- STN-1 USW00094261
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Idleyld Park, OR ( -0.1 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every OR station list.
- Portland-hillsb… (this station) 53°F
- Cold Corvallis, OR 52°F
- Near Idleyld Park, OR 52°F
- Near Foster Dam, OR 52°F
- Near Cottage Grove, OR 52°F
Climate Living Index · Portland-hillsboro
Portland-hillsboro: 80/100 · grade B
Portland-hillsboro publishes 5 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals · NOAA hourly normals); 1 missing weight rescale to 100.
PlainClimate-derived for Portland-hillsboro, not an official NOAA rating. Rankings still use Comfort Score 68/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Normal heat + freeze calendar | 0 calendar days | 100/100 · A |
| Summer moisture balance | 52.1°F mean dew point | 97/100 · A |
| Precipitation balance | 35.9 in · 0.9 from 35 in | 94/100 · A |
| Frost-free season | 190 days/year | 57/100 · C |
| Annual temperature balance | 52.5°F · 15.0° from 67.5°F | 51/100 · D |
Portland-hillsboro · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Portland-hillsboro is a temperate Köppen climate: Csb
Coldest-month mean 39.8°F and warmest-month mean 67.2°F place this station in temperate, dry-summer, warm summer climates (Csb). Class Csb is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: temperate, specifically temperate, dry-summer, warm summer.
- Köppen code
- Csb
- Group
- Temperate
- Warmest month
- 67.2°F
- Coldest month
- 39.8°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Portland-hillsboro sits across the climate record
Three NOAA fields for Portland-hillsboro's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- 51st percentile warmth
- Mid-pack annual mean versus 6,861 station normals.
- Annual precipitation
- 49th percentile wetness
- Neither arid nor torrential versus 6,352 station totals.
- Seasonal temperature swing
- Narrower than 93%
- Warmest-to-coldest month gap for Portland-hillsboro is compact versus 6,861 complete station-years.
How Portland-hillsboro compares across U.S. station-mapped locations
Portland-hillsboro's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
68 Top 44% score exceeds 56% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). Below this entry.
- 30–40: 280 station-mapped locations (5%). Below this entry.
- 40–50: 1,113 station-mapped locations (18%). Below this entry.
- 50–60: 1,329 station-mapped locations (21%). Below this entry.
- 60–70: 1,236 station-mapped locations (20%). This entry sits in this band.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 47°F (8°C) | 34°F (1°C) | 40°F (5°C) | 5.3" | 13.4 | 0.0 |
| February | 51°F (11°C) | 34°F (1°C) | 42°F (6°C) | 4.0" | 12.8 | 0.0 |
| March | 56°F (13°C) | 37°F (3°C) | 46°F (8°C) | 3.7" | 8.6 | 0.0 |
| April | 61°F (16°C) | 39°F (4°C) | 50°F (10°C) | 2.6" | 3.3 | 0.0 |
| May | 69°F (20°C) | 45°F (7°C) | 57°F (14°C) | 2.0" | 0.5 | 0.4 |
| June | 74°F (23°C) | 49°F (9°C) | 61°F (16°C) | 1.3" | 0.0 | 2.0 |
| July | 82°F (28°C) | 52°F (11°C) | 67°F (20°C) | 0.4" | 0.0 | 6.4 |
| August | 82°F (28°C) | 52°F (11°C) | 67°F (19°C) | 0.5" | 0.0 | 6.1 |
| September | 76°F (25°C) | 48°F (9°C) | 62°F (17°C) | 1.4" | 0.1 | 2.3 |
| October | 64°F (18°C) | 41°F (5°C) | 52°F (11°C) | 3.4" | 2.9 | 0.0 |
| November | 53°F (11°C) | 37°F (3°C) | 45°F (7°C) | 5.4" | 8.9 | 0.0 |
| December | 46°F (8°C) | 33°F (1°C) | 40°F (4°C) | 6.0" | 13.7 | 0.0 |
The year, day by day
The calendar barely moves in Portland-hillsboro: no date carries a normal high of 90°F or a normal low at freezing. The year runs between 33°F near December 18 and 84°F near July 27.
No freezing date
Not one calendar date in the 1991–2020 record carries a normal low at or below 32°F. The coldest normal low of the year is 33°F around December 18.
Where the wet dates fall
The likeliest wet date is December 23, when 65% of years recorded at least a hundredth of an inch. The driest is July 27 at 8%. Summed across the calendar, that is about 159 wet dates a year.
The widest day
August 2 carries the biggest normal gap between afternoon and dawn, 31°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Portland-hillsboro.
Monthly Precipitation
Average monthly rainfall
19.3 days with precipitation
16.1 days with precipitation
18.4 days with precipitation
16.0 days with precipitation
12.0 days with precipitation
8.7 days with precipitation
2.9 days with precipitation
3.5 days with precipitation
7.6 days with precipitation
14.9 days with precipitation
19.4 days with precipitation
19.9 days with precipitation
Portland-hillsboro's wet season runs through the cold months
December, January and February carry 43% of the year's precipitation here, while June through August contribute 6%. That is the cool-season-dominant pattern of the West Coast and the higher inland West, where storm tracks swing south in winter and summer turns dry; the thermometer meanwhile shows an unusually narrow 27.4°F seasonal spread.
- Wettest month
- December, 6.0"
- Driest month
- July, 0.4"
- Wettest three months
- December, November, January (47% of the year)
Shares are computed from this station's own 1991-2020 monthly precipitation normals. A cool-season label means the December-February share reaches 35%. Where snow falls, the monthly figures above report liquid-equivalent precipitation, so a wet winter month is not necessarily a rainy one.
How Portland-hillsboro's precipitation splits across the calendar
About 159 days a year record measurable precipitation here, carrying 35.9" between them, or roughly 0.23 inches on a typical wet day. That sits in the middle band: neither the many-light-days pattern of the Pacific Northwest and the Great Lakes, nor the few-heavy-events pattern of the Gulf and the desert Southwest.
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year and say nothing about the heaviest single storm on record.
Frost Dates & Growing Season
First Fall Freeze
October 23
50% probability date
Last Spring Freeze
April 16
50% probability date
Growing Season
190 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
4,830
Higher = more heating needed
Cooling Degree Days
275
Higher = more cooling needed
Warmest Month
July
Coldest Month
December
Humidity & Wind
Monthly averages from hourly observations
| Month | Humidity | Wind (mph) | Clear Sky % | Overcast % |
|---|---|---|---|---|
| January | 83% | 4.7 | 32% | 44% |
| February | 78% | 5.3 | 30% | 39% |
| March | 76% | 5.4 | 29% | 36% |
| April | 70% | 5.3 | 38% | 33% |
| May | 68% | 5.0 | 39% | 31% |
| June | 65% | 5.0 | 55% | 22% |
| July | 61% | 5.0 | 71% | 12% |
| August | 64% | 4.5 | 64% | 13% |
| September | 72% | 3.9 | 57% | 21% |
| October | 82% | 4.0 | 44% | 34% |
| November | 85% | 4.9 | 33% | 45% |
| December | 86% | 4.8 | 28% | 53% |
Nationwide similar cities
Other rankable U.S. places outside OR closest to Portland-hillsboro on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (53°F here).
- Cameron, MO 53°F · 0.0°F off
- Cheraw, CO 53°F · 0.0°F off
- Chillicothe, MO 53°F · 0.0°F off
- Cougar, WA 53°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (35.9" here), excluding temperature-peer places.
- Gonzales, TX 35.9" · 0.0" off
- Ellsworth, WI 35.9" · 0.0" off
- Forest City, IA 35.9" · 0.0" off
- Ionia, MI 35.9" · 0.0" off
Data-derived climate profile
How Portland-hillsboro's climate pattern fits together
heating led · moderate · low swing
Heating is the larger measured load in Portland-hillsboro, at 4,830 degree days versus 275 for cooling. Unlike a strongly continental record, however, its 27.4°F month-to-month range is compact; persistent cool-season demand matters more than a dramatic summer-to-winter reversal.
Portland-hillsboro's frost-free season lasts about 190 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
Temperature varies within a narrow 27.4°F band across the normal year. July and December mark the typical warm and cold ends of the calendar. The annual average is 53°F. Monthly rows still matter, but they refine a steady profile rather than reveal two climatic extremes.
Portland-hillsboro's 35.9 inches of annual precipitation falls in PlainClimate's middle band, so “wet” or “dry” is not the leading description. Snowfall is not added to the interpretation because its annual value is missing. Temperature balance and the calendar distribution carry more information than the annual moisture label alone.
These labels group NOAA 1991-2020 normals from Portland-hillsboro's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Portland-hillsboro, not an official NOAA class or a year-ahead forecast.
Questions about Portland-hillsboro's climate
How much rain does Portland-hillsboro get? ▼
How much energy does heating and cooling require in Portland-hillsboro? ▼
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Portland-hillsboro's primary station: PORTLAND-HILLSBORO AP (USW00094261). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Portland-hillsboro; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Portland-hillsboro comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.