| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 30°F | 49°F | 40°F | 5.8" |
| February | 26°F | 44°F | 35°F | 4.8" |
| March | 34°F | 52°F | 43°F | 6.6" |
| April | 43°F | 62°F | 52°F | 7.0" |
| May | 50°F | 69°F | 60°F | 5.2" |
| June | 64°F | 79°F | 71°F | 7.2" |
| July | 69°F | 85°F | 77°F | 6.9" |
| August | 70°F | 86°F | 78°F | 2.9" |
| September | 62°F | 80°F | 72°F | 2.6" |
| October | 54°F | 71°F | 63°F | 7.4" |
| November | 41°F | 59°F | 50°F | 4.3" |
| December | 32°F | 50°F | 41°F | 6.8" |
| Index | Bethany Beach | Delaware | National |
| Air quality index | 36 | 41 | 42 |
| Pollution index | 7,219,540 | 7,274,307 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 303 |
| Days with moderate air quality | 61 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.060% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.030% |
| Mercury | 0.110% |
| City | Population | Air Quality Index | National Avg. |
| Fenwick Island, DE | 445 | 36 | 28.0% |
| Frankford, DE | 712 | 36 | 28.0% |
| Millville, DE | 1,484 | 36 | 28.0% |
| Ocean City, MD | 6,957 | 36 | 28.0% |
| Berlin, MD | 4,740 | 36 | 28.0% |
| Bethany Beach, DE | 1,150 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Dunnavant, AL | 1,150 | 53 | 6.0% |
| Windsor, IL | 1,150 | 40 | 20.0% |
| Cottage City, MD | 1,150 | 47 | 6.0% |
| Mound City, MO | 1,150 | 43 | 14.0% |
| Ninnekah, OK | 1,150 | 43 | 14.0% |
| Bethany Beach, DE | 1,150 | 36 | 28.0% |
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