| 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 | Syosset | New York | National |
| Air quality index | 51 | 43 | 42 |
| Pollution index | 22,367,000 | 6,179,275 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 169 |
| Days with moderate air quality | 180 |
| Days w/ poor A.Q. for sensitive groups | 16 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.040% |
| Benzene | 0.180% |
| Carbon Tetrachloride | 0.070% |
| Lead | 0.050% |
| Mercury | 0.050% |
| City | Population | Air Quality Index | National Avg. |
| Byram, CT | 4,855 | 43 | 14.0% |
| Old Greenwich, CT | 6,980 | 43 | 14.0% |
| Asharoken, NY | 586 | 43 | 14.0% |
| Eatons Neck, NY | 1,293 | 43 | 14.0% |
| Halesite, NY | 2,483 | 43 | 14.0% |
| Syosset, NY | 19,254 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Murray, KY | 19,254 | 44 | 12.0% |
| Mamaroneck, NY | 19,247 | 51 | 2.0% |
| Sylvania, OH | 19,242 | 40 | 20.0% |
| Arbutus, MD | 19,267 | 46 | 8.0% |
| Mineola, NY | 19,267 | 51 | 2.0% |
| Syosset, NY | 19,254 | 51 | 2.0% |
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