Photo: Jeffrey Beall · CC BY 3.0Few U.S. towns get less rain and snow than Rock River: 13 inches a year
January nights here settle around 12°. Winter nights are cold: in January they are colder than in 91% of U.S. towns. Since 1901–2000, the year has warmed by 1.9°, most of all in March. Comfortable outdoor weather lasts from June to August, with highs of 75–82°.
A year in Rock River at a glance
Each month’s typical high and low, and what it brings.
What stands out about Rock River’s climate
Compared with towns across the U.S., with Rock River’s place in Wyoming beside it.
What a year in Rock River feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 97 frost-free days a year
In half of years the last 32° night comes by June 1 and the first by September 8. Frost and day counts come from NOAA’s station at Medicine Bow, WY, 16 miles from the town’s center, 260 ft lower.
The 2023 USDA map puts Rock River’s center in zone 4b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −25°. 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 52 inches of snow a winter
Snow, measured at Medicine Bow, WY, is heaviest from February through April, about 8 inches a month. 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 85 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Rock River
98% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from September 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 Medicine Bow, WY.
Living with Rock River’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
97 frost-free days in zone 4b. The last frost comes by Jun 1 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 8.
Months with highs of 62–84° and lows of 40° or more: June, July and August. 5.5 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Rock River from natural hazards, river flooding is the largest share (47%); heat waves, cold waves, winter storms and ice storms together are 12%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Rock River and similar climates
TownRatings has no climate map of the towns around Rock River yet.
Climates most like Rock River’s, 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 |
|---|---|---|---|---|
| Rock River, WY | 12° | 82° | 13" | 52" |
| Great Falls, MT | 13° | 84° | 13" | 66" |
| Rexburg, ID | 12° | 84° | 13" | 70" |
| Gleneagle, CO | 14° | 84° | 21" | 55" |
| Taos, NM | 11° | 84° | 13" | 28" |
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 Rock River averaged 1.9° warmer than the 1900s. The biggest change is in March (+4.1°).
A bigger shift than in 86% 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 Rock River compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Rock River’s place among Wyoming’s.
Rock River weather by month
Highs, lows and precipitation from NOAA’s grid at Rock River’s center; snow, wet days and snow on the ground from Medicine Bow, WY. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 33° | 12° | 0.5" | 6.5" | 6 | 16° – 30° |
| February | 35° | 13° | 0.7" | 7.9" | 6 | 18° – 29° |
| March | 45° | 20° | 0.9" | 7.6" | 6 | 25° – 39° |
| April | 53° | 26° | 1.5" | 7.3" | 8 | 33° – 45° |
| May | 63° | 35° | 2.0" | 2.4" | 10 | 43° – 53° |
| June | 75° | 43° | 1.4" | 0.0" | 8 | 53° – 64° |
| July | 82° | 49° | 1.2" | 0.0" | 7 | 60° – 69° |
| August | 80° | 47° | 0.9" | 0.0" | 8 | 59° – 67° |
| September | 71° | 39° | 1.1" | 1.2" | 7 | 50° – 59° |
| October | 57° | 28° | 1.1" | 5.5" | 7 | 35° – 50° |
| November | 43° | 19° | 0.7" | 6.5" | 6 | 19° – 38° |
| December | 33° | 12° | 0.6" | 6.8" | 7 | 16° – 27° |
| Year | 56° | 29° | 12.6" | 51.7" | 85 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 19° to 38°. August is the most reliable, staying within 8°.
Where Rock River’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 Rock River’s center.
- Snow: Medicine Bow, WY.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Medicine Bow, WY, 16 miles from the town’s center, 260 ft lower; 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 Rock River’s climate
What is the weather like in Rock River?
A typical July afternoon reaches 82°, a January night drops to 12°, and about 52 inches of snow falls in a normal winter. Colder January nights than 91% of U.S. towns; cooler July afternoons than 83% of U.S. towns.
How cold does it get in Rock River in winter?
January nights average 12°. About 209 nights a year reach 32° or below and 18 reach 0° or below. In the coldest January of the last 30 years the month averaged 16°.
How much snow does Rock River get?
About 52 inches in a normal winter at Medicine Bow, WY, heaviest from February through April, about 8 inches a month.
How hot does it get in Rock River?
July, with a typical high of 82° and a low of 49°. About 10 days a year reach 90° (Medicine Bow, WY).
When is the first and last frost in Rock River?
In half of years the last spring frost (32°) comes by June 1 and the first fall frost by September 8, about 97 frost-free days, at Medicine Bow, WY.
What growing zone is Rock River in?
Zone 4b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −25°.
What is the best time of year to visit Rock River?
By one simple rule (highs of 62–84° and lows of 40° or more), June, July and August. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Rock River getting warmer?
Yes: 1991–2020 averaged 1.9° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 86% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Rock River.
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.