Photo: Tamanoeconomico · CC BY-SA 4.0Caldwell reaches 100° on about 10 days a year, more than 91% of U.S. towns
A typical July afternoon reaches 93°, a January night drops to 24°, and about 10 inches of snow falls in a normal winter.
A year in Caldwell at a glance
Each month’s typical high and low, and what it brings.
What stands out about Caldwell’s climate
Compared with towns across the U.S., with Caldwell’s place in Idaho beside it.
What a year in Caldwell feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 164 frost-free days a year
In half of years the last 32° night comes by April 29 and the first by October 13. Frost and day counts come from NOAA’s station at Nampa Sugar Factory, ID, 5 miles from the city’s center point, at about the same height.
The 2023 USDA map puts Caldwell’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 4°. 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 10 inches of snow a winter
Snow, measured at Nampa Sugar Factory, ID, falls mostly in December. Precipitation (rain plus melted snow) adds up to 11 inches a year; January is the wettest month and August the driest. Rain or snow falls on about 82 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Caldwell
87% 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 Nampa Sugar Factory, ID.
Living with Caldwell’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
164 frost-free days in zone 7a. The last frost comes by Apr 29 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 13.
Months with highs of 62–84° and lows of 40° or more: May, June and September. 23 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Caldwell from natural hazards, river flooding is the largest share (62%); heat waves, cold waves, winter storms and ice storms together are 20%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Caldwell and similar climates
TownRatings has no climate map of the towns around Caldwell yet.
Climates most like Caldwell’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 |
|---|---|---|---|---|
| Caldwell, ID | 24° | 93° | 11" | 9.7" |
| Rio Rancho, NM | 22° | 92° | 10" | 7.7" |
| Chino Valley, AZ | 27° | 92° | 11" | 10" |
| Spanish Springs, NV | 25° | 91° | 10" | 6.8" |
| Fruitvale, CO | 19° | 94° | 10" | 13" |
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 Caldwell averaged 1.1° warmer than the 1900s. The biggest change is in January (+2.0°).
A smaller shift than in 72% 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 Caldwell compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Caldwell’s place among Idaho’s.
Caldwell weather by month
Highs, lows and precipitation from NOAA’s grid at Caldwell’s center; snow, wet days and snow on the ground from Nampa Sugar Factory, ID. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 39° | 24° | 1.5" | 3.4" | 10 | 5 | 18° – 37° |
| February | 47° | 27° | 0.9" | 1.4" | 7 | 2 | 30° – 44° |
| March | 58° | 33° | 1.1" | 0.2" | 9 | 0 | 41° – 50° |
| April | 65° | 37° | 1.0" | 0.0" | 9 | 0 | 46° – 56° |
| May | 75° | 45° | 1.3" | 0.0" | 8 | 0 | 54° – 65° |
| June | 83° | 52° | 0.7" | 0.0" | 6 | 0 | 63° – 75° |
| July | 93° | 58° | 0.2" | 0.0" | 2 | 0 | 65° – 81° |
| August | 91° | 56° | 0.2" | 0.0" | 2 | 0 | 68° – 76° |
| September | 81° | 47° | 0.4" | 0.0" | 3 | 0 | 60° – 68° |
| October | 66° | 37° | 0.8" | 0.0" | 6 | 0 | 44° – 58° |
| November | 50° | 29° | 1.1" | 0.5" | 10 | 1 | 33° – 45° |
| December | 40° | 24° | 1.4" | 4.2" | 11 | 4 | 22° – 37° |
| Year | 66° | 39° | 10.5" | 9.7" | 82 | 12 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 18° to 37°. September is the most reliable, staying within 8°.
Where Caldwell’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 Caldwell’s center.
- Snow: Nampa Sugar Factory, ID.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Nampa Sugar Factory, ID, 5 miles from the city’s center point, 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 Caldwell’s climate
What is the weather like in Caldwell?
A typical July afternoon reaches 93°, a January night drops to 24°, and about 10 inches of snow falls in a normal winter. Milder January nights than 59% of U.S. towns; hotter July afternoons than 91% of U.S. towns.
How cold does it get in Caldwell in winter?
December nights average 24°. About 132 nights a year reach 32° or below and 1 reach 0° or below. In the coldest December of the last 30 years the month averaged 22°.
How much snow does Caldwell get?
About 9.7 inches in a normal winter at Nampa Sugar Factory, ID, most of it in December, with snow on the ground about 12 days a year.
How hot does it get in Caldwell?
July, with a typical high of 93° and a low of 58°. About 59 days a year reach 90° and 10 reach 100° (Nampa Sugar Factory, ID).
When is the first and last frost in Caldwell?
In half of years the last spring frost (32°) comes by April 29 and the first fall frost by October 13, about 164 frost-free days, at Nampa Sugar Factory, ID.
What growing zone is Caldwell in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 4°.
What is the best time of year to visit Caldwell?
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 Caldwell getting warmer?
Yes: 1991–2020 averaged 1.1° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 72% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Caldwell.
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.