| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 37°F | 29°F | 1.9" |
| February | 21°F | 39°F | 29°F | 1.9" |
| March | 32°F | 53°F | 41°F | 3.6" |
| April | 42°F | 66°F | 53°F | 3.3" |
| May | 52°F | 75°F | 63°F | 3.5" |
| June | 60°F | 83°F | 71°F | 5.3" |
| July | 64°F | 85°F | 74°F | 4.3" |
| August | 62°F | 84°F | 73°F | 2.7" |
| September | 55°F | 78°F | 66°F | 3.7" |
| October | 44°F | 66°F | 54°F | 3.3" |
| November | 33°F | 54°F | 43°F | 2.2" |
| December | 27°F | 42°F | 34°F | 3.0" |
| Index | Delaware | Ohio | National |
| Air quality index | 46 | 40 | 42 |
| Pollution index | 2,158,180 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 237 |
| Days with moderate air quality | 127 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.160% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.003% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Ashley, OH | 1,672 | 41 | 18.0% |
| Cardington, OH | 1,571 | 41 | 18.0% |
| Marengo, OH | 269 | 41 | 18.0% |
| Waldo, OH | 362 | 41 | 18.0% |
| Fulton, OH | 255 | 41 | 18.0% |
| Delaware, OH | 41,818 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Spring Hill, TN | 41,797 | 31 | 38.0% |
| Apache Junction, AZ | 41,863 | 74 | 48.0% |
| Bell Gardens, CA | 41,770 | 72 | 44.0% |
| Timmins, ON | 41,763 | n/a | |
| Midland, MI | 41,922 | 26 | 48.0% |
| Delaware, OH | 41,818 | 46 | 8.0% |
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