| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 42°F | 34°F | 6.3" |
| February | 24°F | 42°F | 32°F | 4.9" |
| March | 31°F | 50°F | 40°F | 7.3" |
| April | 46°F | 67°F | 55°F | 5.0" |
| May | 56°F | 76°F | 65°F | 9.9" |
| June | 64°F | 83°F | 73°F | 8.3" |
| July | 71°F | 87°F | 78°F | 8.3" |
| August | 67°F | 84°F | 75°F | 7.8" |
| September | 61°F | 80°F | 70°F | 4.9" |
| October | 54°F | 72°F | 62°F | 6.3" |
| November | 38°F | 56°F | 46°F | 5.9" |
| December | 33°F | 46°F | 39°F | 5.8" |
| Index | Helmetta | New Jersey | National |
| Air quality index | 41 | 45 | 42 |
| Pollution index | 3,756,270 | 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 | 0.020% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.100% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Blawenburg, NJ | 99 | 41 | 18.0% |
| Franklin Park, NJ | 12,738 | 41 | 18.0% |
| Kendall Park, NJ | 9,852 | 41 | 18.0% |
| Princeton, NJ | 31,161 | 41 | 18.0% |
| Bound Brook, NJ | 10,254 | 41 | 18.0% |
| Helmetta, NJ | 2,232 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Altamont, IL | 2,231 | 40 | 20.0% |
| Bayou L'Ourse, LA | 2,231 | 41 | 18.0% |
| East Uniontown, PA | 2,231 | 36 | 28.0% |
| Cedar Grove, WI | 2,231 | 38 | 24.0% |
| Saint-Damien, QC | 2,231 | n/a | |
| Helmetta, NJ | 2,232 | 41 | 18.0% |
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