| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 48°F | 32°F | 1.2" |
| February | 21°F | 50°F | 34°F | 1.5" |
| March | 30°F | 62°F | 44°F | 1.6" |
| April | 36°F | 66°F | 49°F | 0.2" |
| May | 43°F | 73°F | 57°F | 2.4" |
| June | 54°F | 89°F | 71°F | 1.1" |
| July | 59°F | 92°F | 75°F | 2.1" |
| August | 56°F | 90°F | 72°F | 1.1" |
| September | 49°F | 82°F | 64°F | 0.2" |
| October | 38°F | 69°F | 52°F | 2.1" |
| November | 28°F | 58°F | 41°F | 2.6" |
| December | 17°F | 46°F | 30°F | 0.7" |
| Index | Longmont | Colorado | National |
| Air quality index | 47 | 38 | 42 |
| Pollution index | 1,333,380 | 2,068,342 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 227 |
| Days with moderate air quality | 133 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Mead, CO | 4,978 | 45 | 10.0% |
| Milliken, CO | 7,862 | 45 | 10.0% |
| Johnstown, CO | 14,357 | 45 | 10.0% |
| Platteville, CO | 3,017 | 45 | 10.0% |
| Louisville, CO | 19,342 | 47 | 6.0% |
| Longmont, CO | 95,864 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Riverview, FL | 95,849 | 43 | 14.0% |
| Compton, CA | 95,804 | 72 | 44.0% |
| Brockton, MA | 95,740 | 43 | 14.0% |
| Flint, MI | 95,999 | 38 | 24.0% |
| Brossard, QC | 96,033 | n/a | |
| Longmont, CO | 95,864 | 47 | 6.0% |
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