| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 41°F | 33°F | 2.7" |
| February | 25°F | 42°F | 33°F | 2.3" |
| March | 32°F | 50°F | 40°F | 3.3" |
| April | 42°F | 60°F | 51°F | 3.7" |
| May | 52°F | 70°F | 60°F | 3.4" |
| June | 61°F | 78°F | 69°F | 4.3" |
| July | 68°F | 84°F | 76°F | 3.2" |
| August | 66°F | 83°F | 74°F | 3.4" |
| September | 60°F | 76°F | 68°F | 3.2" |
| October | 50°F | 66°F | 57°F | 3.5" |
| November | 39°F | 55°F | 47°F | 2.5" |
| December | 32°F | 46°F | 39°F | 4.5" |
| Index | Greenlawn | New York | National |
| Air quality index | 43 | 43 | 42 |
| Pollution index | 39,208,800 | 6,179,275 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 262 |
| Days with moderate air quality | 82 |
| Days w/ poor A.Q. for sensitive groups | 18 |
| Days with unhealthy air quality | 3 |
| Pollutant | Total |
| Arsenic | 0.060% |
| Benzene | 0.320% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.320% |
| Mercury | 0.130% |
| City | Population | Air Quality Index | National Avg. |
| Islip, NY | 16,965 | 43 | 14.0% |
| North Great River, NY | 3,396 | 43 | 14.0% |
| West Bay Shore, NY | 4,506 | 43 | 14.0% |
| Islandia, NY | 3,315 | 43 | 14.0% |
| Nissequogue, NY | 1,599 | 43 | 14.0% |
| Greenlawn, NY | 14,598 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Ferndale, WA | 14,591 | 34 | 32.0% |
| Yankton, SD | 14,619 | 36 | 28.0% |
| Homosassa Springs, FL | 14,566 | 30 | 40.0% |
| Thibodaux, LA | 14,565 | 41 | 18.0% |
| Roanoke Rapids, NC | 14,562 | 36 | 28.0% |
| Greenlawn, NY | 14,598 | 43 | 14.0% |
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