| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 27°F | 43°F | 34°F | 3.3" |
| February | 26°F | 43°F | 34°F | 2.5" |
| March | 34°F | 54°F | 43°F | 3.7" |
| April | 44°F | 66°F | 54°F | 4.9" |
| May | 52°F | 74°F | 63°F | 3.2" |
| June | 64°F | 83°F | 73°F | 5.0" |
| July | 68°F | 87°F | 77°F | 5.6" |
| August | 67°F | 86°F | 76°F | 3.7" |
| September | 59°F | 79°F | 69°F | 4.1" |
| October | 48°F | 67°F | 57°F | 6.1" |
| November | 40°F | 57°F | 48°F | 3.3" |
| December | 30°F | 46°F | 38°F | 5.3" |
| Index | Wilmington | Delaware | National |
| Air quality index | 51 | 41 | 42 |
| Pollution index | 2,169,600 | 7,274,307 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 180 |
| Days with moderate air quality | 169 |
| Days w/ poor A.Q. for sensitive groups | 16 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| Quinton, NJ | 369 | 40 | 20.0% |
| Pennsville, NJ | 11,968 | 40 | 20.0% |
| Salem, NJ | 4,761 | 40 | 20.0% |
| Woodstown, NJ | 3,445 | 40 | 20.0% |
| Alloway, NJ | 1,474 | 40 | 20.0% |
| Wilmington, DE | 70,655 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| St. Charles, MO | 70,650 | 54 | 8.0% |
| North Richland Hills, TX | 70,585 | 51 | 2.0% |
| Saint John, NB | 70,776 | n/a | |
| Casas Adobes, AZ | 70,516 | 47 | 6.0% |
| Canton, OH | 70,863 | 46 | 8.0% |
| Wilmington, DE | 70,655 | 51 | 2.0% |
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