Photo: PvtWm · CC BY-SA 4.0Kirby is among the driest of U.S. towns: 10 inches of precipitation a year
On a normal January night the air cools to about 8°. Its January nights bite harder than in 96% of U.S. towns. Warming shows here too: 1.3° more than in 1901–2000, led by January. The frost-free window for a garden runs roughly May 5 to October 5.
A year in Kirby at a glance
Each month’s typical high and low, and what it brings.
What stands out about Kirby’s climate
Compared with towns across the U.S., with Kirby’s place in Wyoming beside it.
What a year in Kirby feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 152 frost-free days a year
In half of years the last 32° night comes by May 5 and the first by October 5. Frost and day counts come from NOAA’s station at Thermopolis, WY, 11 miles from the town’s center, at about the same height.
The 2023 USDA map puts Kirby’s center in zone 4b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −24°. 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 27 inches of snow a winter
Snow, measured at Thermopolis, WY, falls mostly in January and November. Precipitation (rain plus melted snow) adds up to 10 inches a year; May is the wettest month and January the driest. Rain or snow falls on about 59 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Kirby
90% 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 Thermopolis, WY.
Living with Kirby’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
152 frost-free days in zone 4b. The last frost comes by May 5 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 5.
Months with highs of 62–84° and lows of 40° or more: May, June and September.
Parks & trails →Of the yearly building losses FEMA expects in Kirby from natural hazards, river flooding is the largest share (76%); heat waves, cold waves, winter storms and ice storms together are 5%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Kirby and similar climates
TownRatings has no climate map of the towns around Kirby yet.
Climates most like Kirby’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 |
|---|---|---|---|---|
| Kirby, WY | 8° | 91° | 10" | 27" |
| Vernal, UT | 9° | 90° | 9" | 20" |
| Rifle, CO | 14° | 91° | 11" | 27" |
| Elko, NV | 15° | 90° | 10" | 41" |
| Scottsbluff, NE | 15° | 90° | 15" | 43" |
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 Kirby averaged 1.3° warmer than the 1900s. The biggest change is in January (+3.6°).
A smaller 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 Kirby compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Kirby’s place among Wyoming’s.
Kirby weather by month
Highs, lows and precipitation from NOAA’s grid at Kirby’s center; snow, wet days and snow on the ground from Thermopolis, WY. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 33° | 8° | 0.3" | 5.4" | 3 | 22 | 11° – 31° |
| February | 38° | 13° | 0.3" | 4.9" | 4 | 16 | 15° – 36° |
| March | 52° | 24° | 0.6" | 2.3" | 4 | 7 | 28° – 45° |
| April | 60° | 32° | 1.2" | 2.2" | 7 | 1 | 41° – 51° |
| May | 70° | 42° | 2.0" | 0.2" | 8 | 0 | 50° – 62° |
| June | 82° | 50° | 1.1" | 0.0" | 7 | 0 | 59° – 72° |
| July | 91° | 57° | 0.7" | 0.0" | 5 | 0 | 65° – 79° |
| August | 89° | 54° | 0.5" | 0.0" | 4 | 0 | 67° – 75° |
| September | 77° | 44° | 1.0" | 0.3" | 5 | 0 | 56° – 65° |
| October | 62° | 32° | 1.0" | 2.1" | 5 | 1 | 38° – 53° |
| November | 45° | 20° | 0.5" | 5.5" | 4 | 7 | 21° – 42° |
| December | 33° | 9° | 0.3" | 4.5" | 3 | 18 | 12° – 28° |
| Year | 61° | 32° | 9.5" | 27.4" | 59 | 72 |
How much a month can swing
A normal is an average. November swings the most: from 1991 to 2020 its average ranged from 21° to 42°. August is the most reliable, staying within 9°.
Where Kirby’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 Kirby’s center.
- Snow: Thermopolis, WY.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Thermopolis, WY, 11 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 Kirby’s climate
What is the weather like in Kirby?
A typical July afternoon reaches 91°, a January night drops to 8°, and about 27 inches of snow falls in a normal winter. Colder January nights than 96% of U.S. towns; hotter July afternoons than 82% of U.S. towns.
How cold does it get in Kirby in winter?
January nights average 8°. About 168 nights a year reach 32° or below and 14 reach 0° or below. In the coldest January of the last 30 years the month averaged 11°.
How much snow does Kirby get?
About 27 inches in a normal winter at Thermopolis, WY, most of it in January and November, with snow on the ground about 72 days a year.
How hot does it get in Kirby?
July, with a typical high of 91° and a low of 57°. About 55 days a year reach 90° and 4 reach 100° (Thermopolis, WY).
When is the first and last frost in Kirby?
In half of years the last spring frost (32°) comes by May 5 and the first fall frost by October 5, about 152 frost-free days, at Thermopolis, WY.
What growing zone is Kirby in?
Zone 4b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −24°.
What is the best time of year to visit Kirby?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Kirby getting warmer?
Yes: 1991–2020 averaged 1.3° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 55% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Kirby.
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.