Caldwell, Idaho climate: NOAA's gridded normals for the city, beside the nearest station records
NOAA's gridded 1991-2020 normals put Caldwell's center at January lows of 24°F and July highs of 93°F, a yearly mean of 52.3°F and 10.5 inches of precipitation. No NOAA station keeps a record under the city's name. The nearest station record, Nampa (5 miles SE, 2,470 ft), has January lows of 23°F and July highs of 93°F.
73,088 people (Census Bureau 2024). Distances and directions are from the city's center.
- Jan 39° 24°
- Feb 47° 27°
- Mar 58° 33°
- Apr 65° 37°
- May 75° 45°
- Jun 83° 52°
- Jul 93° 58°
- Aug 91° 56°
- Sep 81° 47°
- Oct 66° 37°
- Nov 50° 29°
- Dec 40° 24°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
The months above are NOAA's gridded normals at Caldwell's center.
What is each month like in Caldwell?
NOAA's grid estimates the normals every 5 km or so from the stations around each point, terrain included. It smooths between stations, so night lows at the heart of a large city can run warmer than the grid shows: at five big-city airports we compared, the grid's highs were within about 1°F of the station and its lows 1-6°F cooler. The nearest record's high and low are beside each month.
| Month | High | Low | Mean | Precip. | Nampa high | Nampa low |
|---|---|---|---|---|---|---|
| January | 39°F | 24°F | 31.4°F | 1.45 | 40°F | 23°F |
| February | 47°F | 27°F | 37.2°F | 0.89 | 47°F | 26°F |
| March | 58°F | 33°F | 45.5°F | 1.11 | 57°F | 32°F |
| April | 65°F | 37°F | 51.0°F | 1.03 | 65°F | 36°F |
| May | 75°F | 45°F | 59.8°F | 1.28 | 74°F | 44°F |
| June | 83°F | 52°F | 67.1°F | 0.69 | 83°F | 51°F |
| July | 93°F | 58°F | 75.6°F | 0.20 | 93°F | 57°F |
| August | 91°F | 56°F | 73.7°F | 0.16 | 92°F | 56°F |
| September | 81°F | 47°F | 64.2°F | 0.43 | 81°F | 47°F |
| October | 66°F | 37°F | 51.8°F | 0.77 | 67°F | 37°F |
| November | 50°F | 29°F | 39.4°F | 1.05 | 51°F | 28°F |
| December | 40°F | 24°F | 31.5°F | 1.44 | 40°F | 23°F |
In metric: a yearly mean of 11.3°C, January lows of −5°C, July highs of 34°C and 266 mm of precipitation a year.
Source: NOAA NCEI U.S. Monthly Gridded Climate Normals 1991-2020 (nClimGrid, accession 0245564); NOAA NCEI 1991-2020 station normals. The grid cell holding the city's Census center point.
What do the station records around Caldwell say?
Each row is a NOAA station's own 1991-2020 normals, with the snow and frost dates the grid does not give. A record downhill or nearer the coast than the city can run warmer, one uphill cooler: compare the elevations.
| Record | Where | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| NampaNampa Sugar Factory | 5 mi SE | 2,470 ft | 52.0°F | 23°F | 93°F | 11.0 | 10 | April 29 |
| Deer Flat Dam | 7 mi SW | 2,510 ft | 52.5°F | 25°F | 90°F | 10.0 | – | April 23 |
| Homedale1 mi SE | 13 mi W | 2,230 ft | 51.8°F | 23°F | 92°F | 10.1 | – | April 24 |
Source: NOAA NCEI 1991-2020 U.S. Climate Normals; place center and population: Census Bureau 2024. Last frost: the median last spring date of 32°F.
How much snow, how late a frost, what zone and how much sun in Caldwell?
NOAA's grid gives no snow, frost dates or records, so these come from the nearest station record, Nampa (5 miles SE, 2,470 ft). It gets 10 inches of snow in a normal year. The last spring frost (32°F) comes after April 29 in half of years and the first autumn frost before October 13. Its record high is 109°F (2015) and its record low −26°F (1990) (kept since 1976).
The USDA's 2023 Plant Hardiness Zone Map puts Caldwell in zone 7a (ZIP code 83605).
Over a year 82% of the sunlight that would reach the ground under clear skies gets through the clouds in the area (4.6 kWh per square metre a day, NASA POWER 2001-2020); July is the sunniest month (92%) and December the cloudiest (62%).
Nampa's page has its months, frost probabilities, records by month and recent years. NOAA's grid has monthly figures only, so there are no day-by-day month pages for Caldwell; the nearest record's month pages have them.
Source: NOAA NCEI 1991-2020 normals, station USC00106305; records: ACIS; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; sunshine: NASA POWER.
How does the climate vary across Caldwell, ZIP code by ZIP code?
One ZIP code area lies wholly or partly in Caldwell. Each row also names the nearest station record and its frost dates.
Source: Census Bureau 2020 ZCTA-to-place relationship file and ZCTA centers; NOAA NCEI gridded and station normals, 1991-2020. A ZIP area counts when at least a tenth of its land (and 0.5 km²) is in the city; its figures are the grid cell at its center; frost dates are the nearest record's medians of 32°F.