| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 31°F | 23°F | 1.8" |
| February | 15°F | 32°F | 23°F | 2.0" |
| March | 23°F | 42°F | 32°F | 2.5" |
| April | 35°F | 56°F | 45°F | 2.8" |
| May | 46°F | 69°F | 57°F | 3.9" |
| June | 55°F | 75°F | 64°F | 4.7" |
| July | 59°F | 79°F | 69°F | 6.2" |
| August | 57°F | 77°F | 67°F | 5.1" |
| September | 51°F | 71°F | 60°F | 3.7" |
| October | 41°F | 59°F | 49°F | 4.5" |
| November | 31°F | 47°F | 38°F | 2.0" |
| December | 22°F | 36°F | 28°F | 2.6" |
| Index | Castleton | Vermont | National |
| Air quality index | 36 | 36 | 42 |
| Pollution index | 3,716,800 | 1,478,772 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 322 |
| Days with moderate air quality | 43 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.030% |
| Mercury | 0.004% |
| City | Population | Air Quality Index | National Avg. |
| Fair Haven, VT | 2,273 | 36 | 28.0% |
| Wallingford, VT | 1,029 | 36 | 28.0% |
| Granville, NY | 2,250 | 36 | 28.0% |
| Whitehall, NY | 2,263 | 36 | 28.0% |
| Pittsford, VT | 554 | 36 | 28.0% |
| Castleton, VT | 1,141 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Fayette, IA | 1,141 | 39 | 22.0% |
| Atwater, MN | 1,141 | 32 | 36.0% |
| Palenville, NY | 1,141 | 36 | 28.0% |
| Foreman, AR | 1,142 | 39 | 22.0% |
| Ridgway, CO | 1,142 | 44 | 12.0% |
| Castleton, VT | 1,141 | 36 | 28.0% |
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