| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 6°F | 25°F | 15°F | 6.8" |
| February | 10°F | 31°F | 20°F | 2.6" |
| March | 22°F | 45°F | 33°F | 1.9" |
| April | 34°F | 59°F | 46°F | 2.3" |
| May | 45°F | 70°F | 57°F | 4.2" |
| June | 56°F | 80°F | 68°F | 5.5" |
| July | 60°F | 84°F | 72°F | 3.6" |
| August | 57°F | 81°F | 69°F | 3.9" |
| September | 49°F | 75°F | 61°F | 2.2" |
| October | 36°F | 61°F | 48°F | 2.5" |
| November | 24°F | 46°F | 34°F | 1.2" |
| December | 10°F | 28°F | 19°F | 3.4" |
| Index | Egan | South Dakota | National |
| Air quality index | 42 | 36 | 42 |
| Pollution index | 241,714 | 345,623 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 284 |
| Days with moderate air quality | 76 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Trent, SD | 301 | 36 | 28.0% |
| Chester, SD | 285 | 36 | 28.0% |
| Ihlen, MN | 48 | 36 | 28.0% |
| Colton, SD | 754 | 36 | 28.0% |
| Jasper, MN | 671 | 36 | 28.0% |
| Egan, SD | 279 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Whatley, AL | 279 | 37 | 26.0% |
| Cornfields, AZ | 279 | 17 | 66.0% |
| Garrison, IA | 279 | 39 | 22.0% |
| New Providence, IA | 279 | 37 | 26.0% |
| Harrison, ID | 279 | 43 | 14.0% |
| Egan, SD | 279 | 42 | 16.0% |
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