| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 37°F | 29°F | 4.2" |
| February | 28°F | 47°F | 36°F | 1.6" |
| March | 34°F | 57°F | 44°F | 2.3" |
| April | 37°F | 64°F | 50°F | 2.0" |
| May | 45°F | 74°F | 59°F | 2.8" |
| June | 52°F | 84°F | 67°F | 1.7" |
| July | 59°F | 94°F | 77°F | 3.8" |
| August | 56°F | 92°F | 73°F | 1.7" |
| September | 48°F | 81°F | 63°F | 3.2" |
| October | 38°F | 66°F | 50°F | 3.2" |
| November | 31°F | 51°F | 39°F | 1.9" |
| December | 22°F | 38°F | 29°F | 2.6" |
| Index | Caldwell | Idaho | National |
| Air quality index | 36 | 32 | 42 |
| Pollution index | 9,401,360 | 2,063,710 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 293 |
| Days with moderate air quality | 60 |
| Days w/ poor A.Q. for sensitive groups | 9 |
| Days with unhealthy air quality | 3 |
| Pollutant | Total |
| Arsenic | 0.060% |
| Benzene | 0.130% |
| Carbon Tetrachloride | 0.090% |
| Lead | 0.070% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Kuna, ID | 20,985 | 36 | 28.0% |
| Nampa, ID | 96,825 | 36 | 28.0% |
| Wilder, ID | 1,740 | 36 | 28.0% |
| Marsing, ID | 1,379 | 36 | 28.0% |
| Notus, ID | 594 | 36 | 28.0% |
| Caldwell, ID | 56,734 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Shoreline, WA | 56,835 | 45 | 10.0% |
| Grand Forks, ND | 56,588 | 33 | 34.0% |
| Welland, ON | 56,929 | n/a | |
| Saint-Hyacinthe, QC | 56,946 | n/a | |
| Palm Beach Gardens, FL | 56,979 | 36 | 28.0% |
| Caldwell, ID | 56,734 | 36 | 28.0% |
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