Building at 247 Pleasant Avenue · Photo: Jon Roanhaus · CC BY-SA 4.0Challis sits near the bottom of U.S. towns for precipitation, with 8 inches a year
Midwinter brings lows of about 12°. Winter nights are cold: in January they are colder than in 92% of U.S. towns. Compared with 1901–2000, the average now sits 1.7° higher. Seedlings are safe outdoors from about May 14, with the first autumn frost due around September 25.
A year in Challis at a glance
Each month’s typical high and low, and what it brings.
What stands out about Challis’ climate
Compared with towns across the U.S., with Challis’ place in Idaho beside it.
What a year in Challis 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 14 and the first by September 25. Frost and day counts come from NOAA’s station at Challis Airport, 1.4 miles from the town’s center, 130 ft lower.
The 2023 USDA map puts Challis’ center in zone 5b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −13°. 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 8 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 Challis
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 Challis Airport.
Living with Challis’ climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
131 frost-free days in zone 5b. The last frost comes by May 14 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 25.
Months with highs of 62–84° and lows of 40° or more: June and September. 7.8 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Challis from natural hazards, river flooding is the largest share (48%); heat waves, cold waves, winter storms and ice storms together are 3%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Challis and similar climates
TownRatings has no climate map of the towns around Challis 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 Challis averaged 1.7° warmer than the 1900s. The biggest change is in January (+3.3°).
A bigger shift than in 69% 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 Challis compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Challis’ place among Idaho’s.
Challis weather by month
Highs, lows and precipitation from NOAA’s grid at Challis’ center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 32° | 12° | 0.5" | 13° – 28° |
| February | 38° | 16° | 0.4" | 21° – 34° |
| March | 49° | 24° | 0.6" | 32° – 42° |
| April | 57° | 30° | 0.7" | 38° – 49° |
| May | 67° | 38° | 1.1" | 46° – 59° |
| June | 76° | 45° | 1.2" | 55° – 67° |
| July | 87° | 51° | 0.6" | 59° – 74° |
| August | 85° | 49° | 0.6" | 61° – 71° |
| September | 76° | 41° | 0.7" | 54° – 62° |
| October | 60° | 31° | 0.6" | 37° – 52° |
| November | 42° | 21° | 0.5" | 25° – 39° |
| December | 31° | 11° | 0.7" | 13° – 26° |
| Year | 58° | 31° | 8.0" |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 13° to 28°. September is the most reliable, staying within 8°.
Where Challis’ 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 Challis’ center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Challis Airport, 1.4 miles from the town’s center, 130 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 Challis’ climate
What is the weather like in Challis?
A typical July afternoon reaches 87°, a January night drops to 12°. Colder January nights than 92% of U.S. towns; hotter July afternoons than 63% of U.S. towns.
How cold does it get in Challis in winter?
December nights average 11°. About 193 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 hot does it get in Challis?
July, with a typical high of 87° and a low of 51°. About 28 days a year reach 90° (Challis Airport).
When is the first and last frost in Challis?
In half of years the last spring frost (32°) comes by May 14 and the first fall frost by September 25, about 131 frost-free days, at Challis Airport.
What growing zone is Challis in?
Zone 5b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −13°.
What is the best time of year to visit Challis?
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 Challis getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 69% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Challis.
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.