Boulder Flats sits near the bottom of U.S. towns for winter warmth
Peak summer warmth arrives in July, with afternoons near 87°. The seasons are far apart: from a winter night to a summer afternoon the average spans 79°. It is a dry place: less rain and snow fall here than on 95% of U.S. towns. Seedlings are safe outdoors from about May 18, with the first autumn frost due around September 27.
A year in Boulder Flats at a glance
Each month’s typical high and low, and what it brings.
What stands out about Boulder Flats’ climate
Compared with towns across the U.S., with Boulder Flats’ place in Wyoming beside it.
What a year in Boulder Flats feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 131 frost-free days a year
In half of years the last 32° night comes by May 18 and the first by September 27. Frost and day counts come from NOAA’s station at Lander Hunt Fld Airport, 8 miles from the town’s center, at about the same height.
The 2023 USDA map puts Boulder Flats’ center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −19°. 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 67 inches of snow a winter
Snow, measured at Lander 1n, WY, falls mostly in February, March and December. Precipitation (rain plus melted snow) adds up to 13 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 63 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Boulder Flats
94% 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 Lander Hunt Fld Airport.
Living with Boulder Flats’ climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
131 frost-free days in zone 5a. The last frost comes by May 18 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 and September. 18 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Boulder Flats from natural hazards, river flooding is the largest share (42%); heat waves, cold waves, winter storms and ice storms together are 10%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Boulder Flats and similar climates
TownRatings has no climate map of the towns around Boulder Flats yet.
Climates most like Boulder Flats’, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Boulder Flats, WY | 8° | 87° | 13" | 67" |
| Heber, UT | 12° | 88° | 15" | 75" |
| Rigby, ID | 12° | 85° | 12" | 66" |
| Durango, CO | 12° | 86° | 18" | 64" |
| Great Falls, MT | 13° | 84° | 13" | 66" |
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 Boulder Flats averaged 1.4° warmer than the 1900s. The biggest change is in January (+3.5°).
A bigger shift than in 55% 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 Boulder Flats compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Boulder Flats’ place among Wyoming’s.
Boulder Flats weather by month
Highs, lows and precipitation from NOAA’s grid at Boulder Flats’ center; snow, wet days and snow on the ground from Lander 1n, WY. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 34° | 8° | 0.4" | 6.6" | 4 | 27 | 14° – 27° |
| February | 37° | 12° | 0.6" | 12.3" | 5 | 20 | 15° – 32° |
| March | 49° | 22° | 1.0" | 12.3" | 5 | 10 | 29° – 42° |
| April | 57° | 29° | 1.9" | 10.2" | 7 | 4 | 38° – 49° |
| May | 67° | 38° | 2.8" | 2.7" | 8 | 1 | 46° – 58° |
| June | 78° | 46° | 1.2" | 0.0" | 5 | 0 | 54° – 67° |
| July | 87° | 52° | 0.7" | 0.0" | 4 | 0 | 62° – 73° |
| August | 85° | 51° | 0.6" | 0.0" | 5 | 0 | 64° – 71° |
| September | 74° | 41° | 1.1" | 0.2" | 6 | 1 | 53° – 63° |
| October | 60° | 30° | 1.3" | 5.2" | 5 | 3 | 37° – 51° |
| November | 44° | 18° | 0.7" | 5.5" | 4 | 9 | 20° – 40° |
| December | 33° | 8° | 0.5" | 11.6" | 5 | 18 | 13° – 26° |
| Year | 59° | 30° | 12.8" | 66.6" | 63 | 93 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 20° to 40°. August is the most reliable, staying within 7°.
Where Boulder Flats’ 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 Boulder Flats’ center.
- Snow: Lander 1n, WY.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Lander Hunt Fld Airport, 8 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 Boulder Flats’ climate
What is the weather like in Boulder Flats?
A typical July afternoon reaches 87°, a January night drops to 8°, and about 67 inches of snow falls in a normal winter. Colder January nights than 95% of U.S. towns; hotter July afternoons than 62% of U.S. towns.
How cold does it get in Boulder Flats in winter?
December nights average 8°. About 180 nights a year reach 32° or below and 16 reach 0° or below. In the coldest December of the last 30 years the month averaged 13°.
How much snow does Boulder Flats get?
About 67 inches in a normal winter at Lander 1n, WY, most of it in February, March and December, with snow on the ground about 93 days a year.
How hot does it get in Boulder Flats?
July, with a typical high of 87° and a low of 52°. About 30 days a year reach 90° (Lander Hunt Fld Airport).
When is the first and last frost in Boulder Flats?
In half of years the last spring frost (32°) comes by May 18 and the first fall frost by September 27, about 131 frost-free days, at Lander Hunt Fld Airport.
What growing zone is Boulder Flats in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −19°.
What is the best time of year to visit Boulder Flats?
By one simple rule (highs of 62–84° and lows of 40° or more), June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Boulder Flats getting warmer?
Yes: 1991–2020 averaged 1.4° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 55% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Boulder Flats.
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.