| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 30°F | 43°F | 36°F | 2.2" |
| February | 32°F | 45°F | 37°F | 2.2" |
| March | 39°F | 54°F | 45°F | 3.0" |
| April | 49°F | 65°F | 56°F | 3.1" |
| May | 59°F | 73°F | 65°F | 3.5" |
| June | 69°F | 82°F | 75°F | 4.3" |
| July | 73°F | 85°F | 79°F | 4.8" |
| August | 71°F | 83°F | 77°F | 4.2" |
| September | 66°F | 78°F | 72°F | 3.3" |
| October | 54°F | 67°F | 60°F | 5.0" |
| November | 43°F | 56°F | 49°F | 2.0" |
| December | 36°F | 47°F | 41°F | 3.4" |
| Index | Chester | Maryland | National |
| Air quality index | 46 | 43 | 42 |
| Pollution index | 3,494,010 | 5,342,367 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 223 |
| Days with moderate air quality | 129 |
| Days w/ poor A.Q. for sensitive groups | 13 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| St. Michaels, MD | 1,311 | 41 | 18.0% |
| Grasonville, MD | 3,578 | 41 | 18.0% |
| Queenstown, MD | 950 | 41 | 18.0% |
| Easton, MD | 16,589 | 41 | 18.0% |
| Centreville, MD | 4,829 | 42 | 16.0% |
| Chester, MD | 4,319 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Cornwall, PA | 4,319 | 42 | 16.0% |
| French Island, WI | 4,318 | 35 | 30.0% |
| Grantley, PA | 4,320 | 41 | 18.0% |
| Riva, MD | 4,321 | 47 | 6.0% |
| Barrow, AK | 4,316 | 38 | 24.0% |
| Chester, MD | 4,319 | 46 | 8.0% |
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