| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 7°F | 28°F | 17°F | 1.4" |
| February | 8°F | 29°F | 18°F | 1.6" |
| March | 17°F | 39°F | 28°F | 2.0" |
| April | 31°F | 54°F | 42°F | 2.9" |
| May | 42°F | 67°F | 54°F | 4.2" |
| June | 51°F | 73°F | 62°F | 5.1" |
| July | 55°F | 78°F | 67°F | 5.3" |
| August | 53°F | 76°F | 64°F | 4.7" |
| September | 46°F | 70°F | 57°F | 3.2" |
| October | 37°F | 57°F | 46°F | 4.3" |
| November | 26°F | 45°F | 34°F | 2.4" |
| December | 16°F | 32°F | 24°F | 3.0" |
| Index | Bethlehem | New Hampshire | National |
| Air quality index | 40 | 34 | 42 |
| Pollution index | 1,278,430 | 3,959,618 | 2,726,193 |
| Measurement | Total |
| Days measured | 324 |
| Days with good air quality | 314 |
| Days with moderate air quality | 10 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Mountain Lakes, NH | 643 | 34 | 32.0% |
| Lisbon, NH | 843 | 40 | 20.0% |
| Littleton, NH | 4,294 | 40 | 20.0% |
| Whitefield, NH | 1,202 | 40 | 20.0% |
| Concord, VT | 176 | 40 | 20.0% |
| Bethlehem, NH | 1,061 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Bluewater, AZ | 1,061 | 13 | 74.0% |
| Claypool, AZ | 1,061 | 60 | 20.0% |
| South Pekin, IL | 1,061 | 41 | 18.0% |
| Marion Center, MA | 1,061 | 36 | 28.0% |
| Highlands, NC | 1,061 | 41 | 18.0% |
| Bethlehem, NH | 1,061 | 40 | 20.0% |
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