| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 21°F | 41°F | 31°F | 2.8" |
| February | 22°F | 43°F | 31°F | 2.3" |
| March | 30°F | 53°F | 41°F | 3.7" |
| April | 39°F | 66°F | 52°F | 4.0" |
| May | 49°F | 75°F | 62°F | 3.7" |
| June | 58°F | 83°F | 70°F | 5.3" |
| July | 63°F | 87°F | 75°F | 5.3" |
| August | 61°F | 85°F | 72°F | 5.5" |
| September | 55°F | 79°F | 66°F | 3.6" |
| October | 43°F | 68°F | 55°F | 4.5" |
| November | 33°F | 56°F | 44°F | 3.0" |
| December | 27°F | 46°F | 36°F | 4.6" |
| Index | Middlesex | New Jersey | National |
| Air quality index | 41 | 45 | 42 |
| Pollution index | 5,618,710 | 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 | 0.004% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.040% |
| Mercury | 0.003% |
| City | Population | Air Quality Index | National Avg. |
| Chester, NJ | 1,514 | 34 | 32.0% |
| Long Valley, NJ | 2,327 | 34 | 32.0% |
| Mendham, NJ | 4,880 | 34 | 32.0% |
| Peapack and Gladstone, NJ | 2,582 | 34 | 32.0% |
| Somerset, NJ | 24,119 | 41 | 18.0% |
| Middlesex, NJ | 13,606 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Marshall, MN | 13,604 | 32 | 36.0% |
| Celina, TX | 13,608 | 51 | 2.0% |
| Andover, KS | 13,609 | 40 | 20.0% |
| Canton, IL | 13,600 | 41 | 18.0% |
| Chelsea, AL | 13,599 | 53 | 6.0% |
| Middlesex, NJ | 13,606 | 41 | 18.0% |
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