| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 28°F | 43°F | 36°F | 1.0" |
| February | 30°F | 49°F | 39°F | 1.0" |
| March | 35°F | 57°F | 45°F | 1.6" |
| April | 39°F | 65°F | 51°F | 1.4" |
| May | 46°F | 75°F | 60°F | 1.5" |
| June | 53°F | 82°F | 67°F | 1.3" |
| July | 60°F | 95°F | 77°F | 0.3" |
| August | 59°F | 93°F | 76°F | 0.4" |
| September | 51°F | 82°F | 66°F | 0.6" |
| October | 42°F | 66°F | 53°F | 1.1" |
| November | 33°F | 51°F | 42°F | 1.3" |
| December | 27°F | 41°F | 34°F | 1.4" |
| Index | Lewiston | Idaho | National |
| Air quality index | 29 | 32 | 42 |
| Pollution index | 3,385,410 | 2,063,710 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 291 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.040% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Juliaetta, ID | 511 | 10 | 80.0% |
| Colton, WA | 372 | 18 | 64.0% |
| Lapwai, ID | 1,291 | 29 | 42.0% |
| Clarkston Heights-Vineland, WA | 7,062 | 29 | 42.0% |
| Sweetwater, ID | 264 | 29 | 42.0% |
| Lewiston, ID | 32,853 | 29 | 42.0% |
| City | Population | Air Quality Index | National Avg. |
| Salisbury, MD | 32,850 | 36 | 28.0% |
| Pueblo West, CO | 32,842 | 20 | 60.0% |
| Val-d'Or, QC | 32,869 | n/a | |
| Pikesville, MD | 32,871 | 46 | 8.0% |
| Parkland, FL | 32,878 | 41 | 18.0% |
| Lewiston, ID | 32,853 | 29 | 42.0% |
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