| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 42°F | 33°F | 4.2" |
| February | 25°F | 43°F | 34°F | 3.6" |
| March | 33°F | 52°F | 42°F | 3.9" |
| April | 44°F | 66°F | 54°F | 4.4" |
| May | 53°F | 75°F | 63°F | 4.9" |
| June | 63°F | 84°F | 72°F | 5.3" |
| July | 69°F | 89°F | 78°F | 4.5" |
| August | 66°F | 86°F | 76°F | 5.0" |
| September | 60°F | 81°F | 69°F | 3.5" |
| October | 49°F | 69°F | 58°F | 4.8" |
| November | 38°F | 58°F | 47°F | 3.1" |
| December | 31°F | 47°F | 38°F | 5.0" |
| Index | Old Tappan | New Jersey | National |
| Air quality index | 51 | 45 | 42 |
| Pollution index | 7,043,200 | 7,246,891 | 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 | 0.010% |
| Benzene | 0.050% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.030% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Tuxedo Park, NY | 542 | 36 | 28.0% |
| West Haverstraw, NY | 10,220 | 36 | 28.0% |
| Croton-on-Hudson, NY | 8,121 | 36 | 28.0% |
| Mount Ivy, NY | 7,390 | 36 | 28.0% |
| Crugers, NY | 1,335 | 36 | 28.0% |
| Old Tappan, NJ | 5,924 | 51 | 2.0% |
| City | Population | Air Quality Index | National Avg. |
| Lewistown, MT | 5,923 | 21 | 58.0% |
| Selinsgrove, PA | 5,923 | 35 | 30.0% |
| Woods Creek, WA | 5,922 | 45 | 10.0% |
| Oxford, MA | 5,926 | 40 | 20.0% |
| Margate City, NJ | 5,921 | 37 | 26.0% |
| Old Tappan, NJ | 5,924 | 51 | 2.0% |
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