| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 38°F | 28°F | 2.7" |
| February | 18°F | 38°F | 28°F | 2.7" |
| March | 27°F | 47°F | 36°F | 3.9" |
| April | 37°F | 61°F | 48°F | 3.7" |
| May | 47°F | 71°F | 58°F | 3.7" |
| June | 55°F | 79°F | 66°F | 5.1" |
| July | 62°F | 85°F | 73°F | 4.0" |
| August | 59°F | 83°F | 70°F | 3.6" |
| September | 52°F | 76°F | 63°F | 3.4" |
| October | 41°F | 64°F | 52°F | 4.7" |
| November | 32°F | 53°F | 42°F | 3.5" |
| December | 24°F | 42°F | 33°F | 4.4" |
| Index | Marlborough | Massachusetts | National |
| Air quality index | 40 | 40 | 42 |
| Pollution index | 14,818,200 | 8,399,610 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 312 |
| Days with moderate air quality | 52 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.020% |
| Benzene | 0.150% |
| Carbon Tetrachloride | 0.050% |
| Lead | 0.130% |
| Mercury | 0.040% |
| City | Population | Air Quality Index | National Avg. |
| Milford, MA | 26,072 | 40 | 20.0% |
| Hopkinton, MA | 3,864 | 40 | 20.0% |
| Ayer, MA | 2,551 | 40 | 20.0% |
| Littleton Common, MA | 3,370 | 40 | 20.0% |
| Maynard, MA | 10,900 | 40 | 20.0% |
| Marlborough, MA | 39,663 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Romeoville, IL | 39,644 | 55 | 10.0% |
| Indian Trail, NC | 39,644 | 49 | 2.0% |
| Crystal Lake, IL | 39,685 | 42 | 16.0% |
| Royal Palm Beach, FL | 39,615 | 36 | 28.0% |
| Sumter, SC | 39,758 | 43 | 14.0% |
| Marlborough, MA | 39,663 | 40 | 20.0% |
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