Photo: Andrew Filer · CC BY-SA 2.0Hardly any U.S. towns see harsher January nights than Hillsboro
Expect July afternoons of about 81°. Precipitation is light here, less than falls on 88% of U.S. towns. Decade by decade the climate has edged up, 1.4° above 1901–2000. Picnics, hikes and garden evenings come into their own from May to September, with highs of 68–81°.
A year in Hillsboro at a glance
Each month’s typical high and low, and what it brings.
What stands out about Hillsboro’s climate
Compared with towns across the U.S., with Hillsboro’s place in North Dakota beside it.
What a year in Hillsboro feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 158 frost-free days a year
In half of years the last 32° night comes by May 2 and the first by October 9. Frost and day counts come from NOAA’s station at Hillsboro 3 N, ND, 2.5 miles from the town’s center, at about the same height.
The 2023 USDA map puts Hillsboro’s center in zone 4a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −26°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 23 inches of rain a year
June is the wettest month and February the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Hillsboro
94% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Hillsboro 3 N, ND.
Living with Hillsboro’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
158 frost-free days in zone 4a. The last frost comes by May 2 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 9.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 0.5 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Hillsboro from natural hazards, river flooding is the largest share (51%); heat waves, cold waves, winter storms and ice storms together are 23%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Hillsboro and its neighbors
Every town next door is within a degree of Hillsboro in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Hillsboro averaged 1.4° warmer than the 1900s. The biggest change is in January (+4.0°).
A bigger shift than in 51% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Hillsboro compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Hillsboro’s place among North Dakota’s.
Hillsboro weather by month
Highs, lows and precipitation from NOAA’s grid at Hillsboro’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 17° | 0° | 0.6" | −5° – 24° |
| February | 22° | 4° | 0.6" | −1° – 27° |
| March | 36° | 18° | 1.1" | 17° – 40° |
| April | 53° | 32° | 1.3" | 32° – 51° |
| May | 68° | 44° | 2.9" | 49° – 62° |
| June | 77° | 55° | 3.9" | 62° – 71° |
| July | 81° | 59° | 3.5" | 63° – 76° |
| August | 80° | 56° | 2.8" | 62° – 73° |
| September | 71° | 47° | 2.6" | 54° – 65° |
| October | 55° | 35° | 2.1" | 37° – 51° |
| November | 37° | 20° | 0.8" | 16° – 41° |
| December | 23° | 7° | 0.7" | 2° – 25° |
| Year | 52° | 31° | 22.8" |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from -5° to 24°. June is the most reliable, staying within 9°.
Where Hillsboro’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Hillsboro’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Hillsboro 3 N, ND, 2.5 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Hillsboro’s climate
What is the weather like in Hillsboro?
A typical July afternoon reaches 81°, a January night drops to 0°. Colder January nights than all but 41 U.S. towns; cooler July afternoons than 86% of U.S. towns.
How cold does it get in Hillsboro in winter?
January nights average 0°. About 174 nights a year reach 32° or below and 44 reach 0° or below. In the coldest January of the last 30 years the month averaged −5°.
How hot does it get in Hillsboro?
July, with a typical high of 81° and a low of 59°. About 10 days a year reach 90° (Hillsboro 3 N, ND).
When is the first and last frost in Hillsboro?
In half of years the last spring frost (32°) comes by May 2 and the first fall frost by October 9, about 158 frost-free days, at Hillsboro 3 N, ND.
What growing zone is Hillsboro in?
Zone 4a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −26°.
What is the best time of year to visit Hillsboro?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Hillsboro getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 51% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Hillsboro.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.