Anna Nielsen Scofield House · Photo: Tricia Simpson · CC BY-SA 3.0Hardly any U.S. towns see harsher January nights than St. Charles
In July the day’s top temperature is typically 84°. The year swings widely: the coldest month’s nights and the warmest month’s afternoons are 76° apart. By precipitation alone, it ranks drier than 94% of U.S. towns. Garden planting can start around May 19; autumn frost returns near September 21.
A year in St. Charles at a glance
Each month’s typical high and low, and what it brings.
What stands out about St. Charles’ climate
Compared with towns across the U.S., with St. Charles’ place in Idaho beside it.
What a year in St. Charles feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 123 frost-free days a year
In half of years the last 32° night comes by May 19 and the first by September 21. Frost and day counts come from NOAA’s station at Lifton Pumping Stn, ID, 4 miles from the town’s center, at about the same height.
The 2023 USDA map puts St. Charles’ 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 37 inches of snow a winter
Snow, measured at Lifton Pumping Stn, ID, is heaviest from January through February, about 9 inches a month. Precipitation (rain plus melted snow) adds up to 14 inches a year; May is the wettest month and July the driest. Rain or snow falls on about 89 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in St. Charles
99% 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 Lifton Pumping Stn, ID.
Living with St. Charles’ climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
123 frost-free days in zone 5a. The last frost comes by May 19 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 21.
Months with highs of 62–84° and lows of 40° or more: June, July and August.
Parks & trails →Of the yearly building losses FEMA expects in St. Charles from natural hazards, avalanches are the largest share (43%); heat waves, cold waves, winter storms and ice storms together are 5%. Normals are averages; the hazards page covers the extremes.
Natural hazards →St. Charles and similar climates
TownRatings has no climate map of the towns around St. Charles yet.
Climates most like St. Charles’, 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 |
|---|---|---|---|---|
| St. Charles, ID | 8° | 84° | 14" | 37" |
| Dickinson, ND | 5° | 83° | 16" | 35" |
| Havre, MT | 6° | 85° | 13" | 41" |
| Taos, NM | 11° | 84° | 13" | 28" |
| Gypsum, CO | 11° | 86° | 14" | 39" |
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 St. Charles averaged 1.6° warmer than the 1900s. The biggest change is in March (+3.6°).
A bigger shift than in 66% 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 St. Charles compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with St. Charles’ place among Idaho’s.
St. Charles weather by month
Highs, lows and precipitation from NOAA’s grid at St. Charles’ center; snow, wet days and snow on the ground from Lifton Pumping Stn, ID. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 30° | 8° | 1.3" | 9.1" | 8 | 29 | 12° – 27° |
| February | 33° | 10° | 1.2" | 8.8" | 9 | 26 | 16° – 30° |
| March | 43° | 20° | 1.1" | 4.1" | 9 | 19 | 25° – 38° |
| April | 53° | 27° | 1.4" | 2.7" | 9 | 3 | 33° – 46° |
| May | 63° | 35° | 1.9" | 0.2" | 10 | 0 | 43° – 54° |
| June | 73° | 41° | 1.0" | 0.0" | 6 | 0 | 51° – 63° |
| July | 84° | 48° | 0.6" | 0.0" | 4 | 0 | 56° – 70° |
| August | 82° | 46° | 0.8" | 0.0" | 5 | 0 | 59° – 67° |
| September | 72° | 37° | 1.2" | 0.1" | 6 | 0 | 51° – 59° |
| October | 58° | 28° | 1.3" | 1.1" | 7 | 1 | 34° – 48° |
| November | 42° | 19° | 1.1" | 4.1" | 8 | 7 | 23° – 36° |
| December | 31° | 10° | 1.2" | 7.2" | 8 | 22 | 15° – 26° |
| Year | 55° | 27° | 13.9" | 37.4" | 89 | 107 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 12° to 27°. September is the most reliable, staying within 8°.
Where St. Charles’ 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 St. Charles’ center.
- Snow: Lifton Pumping Stn, ID.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Lifton Pumping Stn, ID, 4 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 St. Charles’ climate
What is the weather like in St. Charles?
A typical July afternoon reaches 84°, a January night drops to 8°, and about 37 inches of snow falls in a normal winter. Colder January nights than 96% of U.S. towns; cooler July afternoons than 65% of U.S. towns.
How cold does it get in St. Charles in winter?
January nights average 8°. About 202 nights a year reach 32° or below and 26 reach 0° or below. In the coldest January of the last 30 years the month averaged 12°.
How much snow does St. Charles get?
About 37 inches in a normal winter at Lifton Pumping Stn, ID, heaviest from January through February, about 9 inches a month, with snow on the ground about 107 days a year.
How hot does it get in St. Charles?
July, with a typical high of 84° and a low of 48°. About 5 days a year reach 90° (Lifton Pumping Stn, ID).
When is the first and last frost in St. Charles?
In half of years the last spring frost (32°) comes by May 19 and the first fall frost by September 21, about 123 frost-free days, at Lifton Pumping Stn, ID.
What growing zone is St. Charles 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 St. Charles?
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 St. Charles getting warmer?
Yes: 1991–2020 averaged 1.6° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 66% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in St. Charles.
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.