Climate averages 1991–2020
Nampa weather
by month.
See how the year changes. July has the highest average daily maximum; July (tied with August) has the lowest average monthly rainfall.
Pleasant-weather months by our simple rule: MayJuneSeptemberOctober
Long-term climate patterns, not a forecast for a particular trip.
Across the year Nampa averages a daytime high of 18.0°C and a nighttime low of 6.7°C, with about 279 mm of rain on roughly 65 days. July is the warmest month (average high 33.3°C) and December the coolest (4.4°C). December is the wettest month with 42 mm; July (tied with August) is the driest with 3.4 mm.
Months with pleasant weather by a simple rule (average high between 18°C and 29°C, average low of at least 5°C and at most 8 rain days): May, June, September and October. This looks at temperature and rain only, not humidity, wind, sea temperature or crowds.
The annual picture
A year in Nampa
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Nampa climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 4.6°C-3.4°C | -3.4°C | 40 | 9.0 | 9.39 h |
| February | 7.7°C-1.9°C | -1.9°C | 26 | 7.4 | 10.510 h |
| March | 12.8°C1.5°C | 1.5°C | 31 | 8.6 | 11.912 h |
| April | 16.8°C4.7°C | 4.7°C | 28 | 6.4 | 13.413 h |
| May | 22.4°C9.8°C | 9.8°C | 29 | 5.9 | 14.715 h |
| June | 27.3°C14.2°C | 14.2°C | 16 | 3.4 | 15.415 h |
| July | 33.3°C19.2°C | 19.2°C | 3.4 | 1.0 | 15.115 h |
| August | 32.3°C18.3°C | 18.3°C | 3.4 | 0.9 | 14.014 h |
| September | 26.5°C13.4°C | 13.4°C | 9.8 | 2.0 | 12.613 h |
| October | 18.2°C6.9°C | 6.9°C | 20 | 4.2 | 11.111 h |
| November | 9.9°C0.9°C | 0.9°C | 30 | 7.3 | 9.710 h |
| December | 4.4°C-2.9°C | -2.9°C | 42 | 9.3 | 9.09 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
Nearby cities
- MeridianUnited States · 16 kmHigh 17.4°C · Low 5.8°C · 279 mm rain a year
- BoiseUnited States · 30 kmHigh 17.3°C · Low 5.8°C · 311 mm rain a year
- KennewickUnited States · 360 kmHigh 19.2°C · Low 7.8°C · 228 mm rain a year
- Tri-CitiesUnited States · 365 kmHigh 19.4°C · Low 7.9°C · 228 mm rain a year
- BendUnited States · 386 kmHigh 14.2°C · Low 2.3°C · 544 mm rain a year
- MissoulaUnited States · 422 kmHigh 13.4°C · Low 3.1°C · 508 mm rain a year
- OgdenUnited States · 457 kmHigh 15.4°C · Low 3.8°C · 503 mm rain a year
- YakimaUnited States · 460 kmHigh 16.3°C · Low 4.7°C · 341 mm rain a year
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsWhat do the high and low temperatures mean?
We average the daily maximum and daily minimum for each calendar month over 1991–2020. They are not record extremes, a forecast range or temperatures at a fixed time of day.
How is a rain day counted?
A local calendar day (standard time, UTC-7, no daylight saving) with at least 1 mm of total precipitation counts as one rain day. We count these for each year and month, then average across 30 years. The average does not predict which days will be wet.
Where do the numbers come from?
ERA5-Land (temperature) and ERA5 (precipitation) reanalysis from the Copernicus Climate Change Service, read from the Open-Meteo open-data archive. Temperature comes from the 0.1° model cell at 43.50°, -116.60° (5 km from the city centre), adjusted up by 0.1°C for the difference between the city's elevation (767 m) and the cell's (784 m). Rain comes from the 0.25° cell at 43.50°, -116.50°. Meridian lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells. These are model estimates, not weather-station readings; coast, hills and city streets can differ.
Does this page show sunshine, humidity or sea temperature?
No. The data used here contain air temperature and precipitation only. Daylight hours are calculated from the city's latitude (sunrise to sunset), not measured sunshine.