| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | -3°F | 16°F | 6°F | 19.8" |
| February | -2°F | 18°F | 7°F | 6.0" |
| March | 14°F | 33°F | 23°F | 3.3" |
| April | 30°F | 53°F | 40°F | 1.1" |
| May | 41°F | 67°F | 53°F | 3.3" |
| June | 52°F | 76°F | 63°F | 4.2" |
| July | 56°F | 81°F | 68°F | 2.7" |
| August | 53°F | 80°F | 66°F | 2.2" |
| September | 46°F | 73°F | 58°F | 2.6" |
| October | 34°F | 56°F | 44°F | 1.9" |
| November | 19°F | 37°F | 27°F | 1.3" |
| December | 2°F | 19°F | 10°F | 9.7" |
| Index | Walhalla | North Dakota | National |
| Air quality index | 33 | 35 | 42 |
| Pollution index | 536,122 | 1,038,665 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 327 |
| Days with moderate air quality | 34 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.020% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| Cavalier, ND | 1,328 | 33 | 34.0% |
| Walhalla, ND | 896 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Courtland, AL | 896 | 41 | 18.0% |
| Clay City, IL | 896 | 40 | 20.0% |
| Buras, LA | 896 | 45 | 10.0% |
| Cankton, LA | 896 | 41 | 18.0% |
| Cass Lake, MN | 896 | 29 | 42.0% |
| Walhalla, ND | 896 | 33 | 34.0% |
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