| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 36°F | 24°F | 0.9" |
| February | 17°F | 38°F | 26°F | 1.0" |
| March | 28°F | 52°F | 38°F | 2.4" |
| April | 38°F | 62°F | 48°F | 5.9" |
| May | 48°F | 72°F | 59°F | 5.6" |
| June | 59°F | 82°F | 70°F | 6.4" |
| July | 64°F | 88°F | 75°F | 5.6" |
| August | 61°F | 84°F | 72°F | 6.9" |
| September | 52°F | 78°F | 63°F | 6.3" |
| October | 40°F | 64°F | 50°F | 5.7" |
| November | 27°F | 51°F | 38°F | 2.0" |
| December | 16°F | 35°F | 25°F | 1.2" |
| Index | Fairfax | South Dakota | National |
| Air quality index | 36 | 36 | 42 |
| Pollution index | 179,967 | 345,623 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 321 |
| Days with moderate air quality | 43 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.002% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Naper, NE | 83 | 36 | 28.0% |
| Spencer, NE | 345 | 36 | 28.0% |
| Anoka, NE | 35 | 36 | 28.0% |
| Bonesteel, SD | 386 | 36 | 28.0% |
| Butte, NE | 348 | 36 | 28.0% |
| Fairfax, SD | 138 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Reader, AR | 138 | 32 | 36.0% |
| Winchester, AR | 138 | 43 | 14.0% |
| Jackson Lake, CO | 138 | 45 | 10.0% |
| Trail Side, CO | 138 | 45 | 10.0% |
| Jersey, GA | 138 | 44 | 12.0% |
| Fairfax, SD | 138 | 36 | 28.0% |
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