| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 1°F | 19°F | 10°F | 0.6" |
| February | 2°F | 20°F | 10°F | 0.5" |
| March | 17°F | 36°F | 26°F | 3.3" |
| April | 31°F | 54°F | 41°F | 3.2" |
| May | 43°F | 68°F | 55°F | 8.4" |
| June | 54°F | 77°F | 65°F | 6.0" |
| July | 58°F | 83°F | 70°F | 6.1" |
| August | 55°F | 81°F | 67°F | 5.6" |
| September | 47°F | 72°F | 59°F | 5.5" |
| October | 35°F | 56°F | 45°F | 5.3" |
| November | 21°F | 39°F | 29°F | 3.2" |
| December | 4°F | 21°F | 12°F | 2.0" |
| Index | Grafton | 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. |
| Conway, ND | 13 | 33 | 34.0% |
| Drayton, ND | 803 | 33 | 34.0% |
| Forest River, ND | 132 | 33 | 34.0% |
| Crystal, ND | 94 | 33 | 34.0% |
| Nash, ND | 35 | 33 | 34.0% |
| Grafton, ND | 4,139 | 33 | 34.0% |
| City | Population | Air Quality Index | National Avg. |
| Haleyville, AL | 4,139 | 37 | 26.0% |
| North Wilkesboro, NC | 4,139 | 26 | 48.0% |
| Falls City, NE | 4,139 | 43 | 14.0% |
| Northwest Harbor, NY | 4,138 | 37 | 26.0% |
| Broadmoor, CA | 4,140 | 43 | 14.0% |
| Grafton, ND | 4,139 | 33 | 34.0% |
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