Less rain and snow falls on Harrison than on 93% of U.S. towns: 16 inches a year
Midwinter brings lows of about 16°. Its January nights bite harder than in 79% of U.S. towns. Warming shows here too: 1.4° more than in 1901–2000, led by January. Homes need heating from October to April, the months averaging under 50°.
A year in Harrison at a glance
Each month’s typical high and low, and what it brings.
What stands out about Harrison’s climate
Compared with towns across the U.S., with Harrison’s place in Montana beside it.
What a year in Harrison feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 139 frost-free days a year
In half of years the last 32° night comes by May 9 and the first by September 27. Day counts come from NOAA’s station at Norris Madison Pwr House, MT, 17 miles from the town’s center, 130 ft lower; frost dates and degree days from Trident, MT, 22 miles away.
The 2023 USDA map puts Harrison’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −17°. 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 16 inches of rain a year
June is the wettest month and January the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Harrison
96% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through May.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Trident, MT.
Living with Harrison’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
139 frost-free days in zone 5a. The last frost comes by May 9 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Sep 27.
Months with highs of 62–84° and lows of 40° or more: June, July, August and September.
Parks & trails →Of the yearly building losses FEMA expects in Harrison from natural hazards, avalanches are the largest share (67%); heat waves, cold waves, winter storms and ice storms together are 5%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Harrison and similar climates
TownRatings has no climate map of the towns around Harrison yet.
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Harrison averaged 1.4° warmer than the 1900s. The biggest change is in January (+4.2°).
A bigger shift than in 52% 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 Harrison compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Harrison’s place among Montana’s.
Harrison weather by month
Highs, lows and precipitation from NOAA’s grid at Harrison’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 37° | 16° | 0.5" | 18° – 33° |
| February | 39° | 17° | 0.6" | 17° – 37° |
| March | 48° | 24° | 1.1" | 29° – 42° |
| April | 55° | 30° | 1.9" | 37° – 47° |
| May | 65° | 38° | 2.6" | 46° – 56° |
| June | 73° | 44° | 2.6" | 54° – 65° |
| July | 84° | 49° | 1.3" | 57° – 73° |
| August | 83° | 47° | 1.1" | 59° – 69° |
| September | 72° | 40° | 1.5" | 52° – 61° |
| October | 58° | 31° | 1.3" | 37° – 51° |
| November | 44° | 22° | 0.7" | 25° – 42° |
| December | 35° | 15° | 0.6" | 18° – 30° |
| Year | 58° | 31° | 15.6" |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 17° to 37°. September is the most reliable, staying within 8°.
Where Harrison’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 Harrison’s center.
- Frost dates, heating and cooling: Trident, MT, 22 miles away.
- Freezing nights, 90° and 100° days: Norris Madison Pwr House, MT, 17 miles from the town’s center, 130 ft lower; no station nearby passes every check; this is the nearest one in the same valley, flagged above.
- 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 Harrison’s climate
What is the weather like in Harrison?
A typical July afternoon reaches 84°, a January night drops to 16°. Colder January nights than 79% of U.S. towns; cooler July afternoons than 64% of U.S. towns.
How cold does it get in Harrison in winter?
December nights average 15°. About 127 nights a year reach 32° or below and 5 reach 0° or below. In the coldest December of the last 30 years the month averaged 18°.
How hot does it get in Harrison?
July, with a typical high of 84° and a low of 49°. About 21 days a year reach 90° (Trident, MT).
When is the first and last frost in Harrison?
In half of years the last spring frost (32°) comes by May 9 and the first fall frost by September 27, about 139 frost-free days, at Trident, MT.
What growing zone is Harrison in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −17°.
What is the best time of year to visit Harrison?
By one simple rule (highs of 62–84° and lows of 40° or more), June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Harrison getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 52% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Harrison.
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.