| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 35°F | 24°F | 0.8" |
| February | 18°F | 37°F | 27°F | 1.3" |
| March | 32°F | 54°F | 41°F | 2.5" |
| April | 42°F | 65°F | 52°F | 4.9" |
| May | 52°F | 73°F | 62°F | 5.8" |
| June | 63°F | 83°F | 72°F | 6.1" |
| July | 66°F | 87°F | 76°F | 3.9" |
| August | 64°F | 84°F | 74°F | 6.4" |
| September | 56°F | 77°F | 66°F | 3.7" |
| October | 44°F | 65°F | 54°F | 3.3" |
| November | 33°F | 52°F | 41°F | 2.2" |
| December | 21°F | 38°F | 28°F | 2.0" |
| Index | Delphos | Iowa | National |
| Air quality index | 43 | 39 | 42 |
| Pollution index | 1,369,890 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 283 |
| Days with moderate air quality | 82 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Ellston, IA | 37 | 39 | 22.0% |
| Sun Valley Lake, IA | 188 | 39 | 22.0% |
| Mount Ayr, IA | 1,988 | 39 | 22.0% |
| Tingley, IA | 105 | 39 | 22.0% |
| Clearfield, IA | 429 | 39 | 22.0% |
| Delphos, IA | 44 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Ocotillo, CA | 44 | 58 | 16.0% |
| Whitley Gardens, CA | 44 | 46 | 8.0% |
| Crestone, CO | 44 | 16 | 68.0% |
| Lynn, CO | 44 | 20 | 60.0% |
| Fenwick, CT | 44 | 37 | 26.0% |
| Delphos, IA | 44 | 43 | 14.0% |
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