| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 38°F | 27°F | 5.0" |
| February | 16°F | 37°F | 25°F | 4.6" |
| March | 24°F | 45°F | 34°F | 7.3" |
| April | 36°F | 60°F | 47°F | 9.2" |
| May | 45°F | 68°F | 56°F | 7.8" |
| June | 56°F | 81°F | 67°F | 3.2" |
| July | 61°F | 85°F | 72°F | 4.2" |
| August | 61°F | 86°F | 72°F | 4.0" |
| September | 53°F | 79°F | 65°F | 3.1" |
| October | 45°F | 65°F | 54°F | 9.5" |
| November | 31°F | 53°F | 41°F | 4.7" |
| December | 20°F | 38°F | 29°F | 5.5" |
| Index | Waltham | Massachusetts | National |
| Air quality index | 43 | 40 | 42 |
| Pollution index | 7,556,320 | 8,399,610 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 291 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.070% |
| Carbon Tetrachloride | 0.040% |
| Lead | 0.010% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Framingham, MA | 72,846 | 40 | 20.0% |
| Hopkinton, MA | 3,864 | 40 | 20.0% |
| Littleton Common, MA | 3,370 | 40 | 20.0% |
| Maynard, MA | 10,900 | 40 | 20.0% |
| Cordaville, MA | 2,884 | 40 | 20.0% |
| Waltham, MA | 62,597 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Pico Rivera, CA | 62,507 | 72 | 44.0% |
| Montebello, CA | 62,697 | 72 | 44.0% |
| Coon Rapids, MN | 62,706 | 46 | 8.0% |
| North Miami, FL | 62,468 | 41 | 18.0% |
| Springfield, OR | 62,729 | 38 | 24.0% |
| Waltham, MA | 62,597 | 43 | 14.0% |
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