| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 12°F | 34°F | 20°F | 0.6" |
| February | 15°F | 35°F | 23°F | 0.9" |
| March | 27°F | 54°F | 38°F | 1.4" |
| April | 34°F | 59°F | 45°F | 2.9" |
| May | 44°F | 69°F | 55°F | 5.2" |
| June | 55°F | 81°F | 67°F | 6.0" |
| July | 63°F | 93°F | 76°F | 9.1" |
| August | 59°F | 87°F | 71°F | 3.5" |
| September | 51°F | 82°F | 64°F | 1.5" |
| October | 39°F | 65°F | 49°F | 3.1" |
| November | 26°F | 50°F | 35°F | 0.9" |
| December | 14°F | 33°F | 22°F | 1.3" |
| Index | Isabel | South Dakota | National |
| Air quality index | 36 | 36 | 42 |
| Pollution index | 308,702 | 345,623 | 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 | 0.004% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Isabel, SD | 196 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Stevinson, CA | 196 | 48 | 4.0% |
| Trowbridge, CA | 196 | 44 | 12.0% |
| Yolo, CA | 196 | 52 | 4.0% |
| Du Pont, GA | 196 | 35 | 30.0% |
| Leighton, IA | 196 | 39 | 22.0% |
| Isabel, SD | 196 | 36 | 28.0% |
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