| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 42°F | 33°F | 3.3" |
| February | 25°F | 43°F | 34°F | 2.4" |
| March | 33°F | 53°F | 42°F | 3.4" |
| April | 43°F | 66°F | 54°F | 3.8" |
| May | 52°F | 75°F | 63°F | 3.9" |
| June | 62°F | 83°F | 72°F | 5.3" |
| July | 67°F | 88°F | 77°F | 5.1" |
| August | 65°F | 85°F | 75°F | 4.7" |
| September | 59°F | 79°F | 68°F | 3.5" |
| October | 48°F | 68°F | 57°F | 4.2" |
| November | 37°F | 57°F | 46°F | 2.9" |
| December | 31°F | 47°F | 38°F | 4.3" |
| Index | Princeton | New Jersey | National |
| Air quality index | 41 | 45 | 42 |
| Pollution index | 3,313,920 | 7,246,891 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 280 |
| Days with moderate air quality | 83 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.350% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.350% |
| Mercury | 0.340% |
| City | Population | Air Quality Index | National Avg. |
| Blackwells Mills, NJ | 9,509 | 41 | 18.0% |
| East Rocky Hill, NJ | 335 | 41 | 18.0% |
| Heathcote, NJ | 7,389 | 41 | 18.0% |
| Lambertville, NJ | 3,809 | 41 | 18.0% |
| Six Mile Run, NJ | 3,432 | 41 | 18.0% |
| Princeton, NJ | 31,161 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Needham, MA | 31,177 | 43 | 14.0% |
| Michigan City, IN | 31,191 | 37 | 26.0% |
| Naugatuck, CT | 31,201 | 41 | 18.0% |
| Centereach, NY | 31,100 | 43 | 14.0% |
| Sherwood, AR | 31,225 | 45 | 10.0% |
| Princeton, NJ | 31,161 | 41 | 18.0% |
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