| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 3°F | 27°F | 15°F | 0.5" |
| February | 6°F | 31°F | 17°F | 0.5" |
| March | 19°F | 46°F | 31°F | 0.8" |
| April | 30°F | 60°F | 44°F | 1.6" |
| May | 40°F | 71°F | 55°F | 3.0" |
| June | 51°F | 81°F | 66°F | 3.8" |
| July | 57°F | 89°F | 73°F | 2.7" |
| August | 54°F | 86°F | 69°F | 3.1" |
| September | 45°F | 78°F | 60°F | 1.7" |
| October | 33°F | 61°F | 46°F | 1.4" |
| November | 19°F | 46°F | 31°F | 0.7" |
| December | 6°F | 28°F | 16°F | 1.2" |
| Index | Harmon | North Dakota | National |
| Air quality index | 36 | 35 | 42 |
| Pollution index | 1,180,610 | 1,038,665 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 320 |
| Days with moderate air quality | 45 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Bismarck, ND | 73,435 | 36 | 28.0% |
| Lincoln, ND | 4,140 | 36 | 28.0% |
| Mandan, ND | 22,482 | 36 | 28.0% |
| Wilton, ND | 725 | 36 | 28.0% |
| Harmon, ND | 228 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Fruitdale, AL | 228 | 42 | 16.0% |
| Grady, AR | 228 | 45 | 10.0% |
| Griffithville, AR | 228 | 45 | 10.0% |
| Everglades, FL | 228 | 34 | 32.0% |
| Arthur, IA | 228 | 35 | 30.0% |
| Harmon, ND | 228 | 36 | 28.0% |
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