| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 35°F | 27°F | 2.3" |
| February | 20°F | 37°F | 28°F | 2.3" |
| March | 31°F | 51°F | 40°F | 3.2" |
| April | 41°F | 64°F | 52°F | 4.1" |
| May | 51°F | 74°F | 63°F | 4.3" |
| June | 61°F | 82°F | 71°F | 4.8" |
| July | 63°F | 85°F | 74°F | 3.5" |
| August | 61°F | 83°F | 72°F | 3.9" |
| September | 54°F | 78°F | 65°F | 2.7" |
| October | 44°F | 66°F | 54°F | 2.9" |
| November | 34°F | 53°F | 43°F | 2.7" |
| December | 26°F | 40°F | 33°F | 3.1" |
| Index | Delphos | Ohio | National |
| Air quality index | 39 | 40 | 50 |
| Pollution index | 850,677 | 6,740,001 | 5,066,862 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 303 |
| Days with moderate air quality | 61 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Glandorf, OH | 927 | 39 | 22% |
| Fort Jennings, OH | 483 | 39 | 22% |
| Lima, OH | 37,836 | 39 | 22% |
| Ohio City, OH | 805 | 39 | 22% |
| Van Wert, OH | 10,738 | 39 | 22% |
| Delphos, OH | 7,216 | 39 | 22% |
| City, State | Population | Air Quality Index | National Avg. |
| Delafield, WI | 7,218 | 37 | 26% |
| Oroville East, CA | 7,218 | 46 | 8% |
| Bel Aire, KS | 7,214 | 40 | 20% |
| Rockland, ME | 7,220 | 36 | 28% |
| Riverdale Park, MD | 7,221 | 47 | 6% |
| Delphos, OH | 7,216 | 39 | 22% |
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