| 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 | Napoleon | North Dakota | National |
| Air quality index | 36 | 35 | 42 |
| Pollution index | 191,435 | 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 | 0.003% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Napoleon, ND | 787 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Allentown, FL | 787 | 41 | 18.0% |
| St. Charles, IA | 787 | 39 | 22.0% |
| Wadsworth, NV | 787 | 39 | 22.0% |
| McClure, OH | 787 | 40 | 20.0% |
| Twinsburg Heights, OH | 787 | 43 | 14.0% |
| Napoleon, ND | 787 | 36 | 28.0% |
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