| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 43°F | 29°F | 2.6" |
| February | 20°F | 47°F | 32°F | 0.5" |
| March | 28°F | 59°F | 42°F | 1.4" |
| April | 34°F | 64°F | 47°F | 3.7" |
| May | 43°F | 71°F | 55°F | 4.4" |
| June | 52°F | 85°F | 68°F | 2.1" |
| July | 57°F | 90°F | 72°F | 2.6" |
| August | 56°F | 87°F | 71°F | 2.6" |
| September | 50°F | 81°F | 64°F | 1.8" |
| October | 38°F | 66°F | 50°F | 2.2" |
| November | 27°F | 55°F | 39°F | 1.2" |
| December | 16°F | 42°F | 27°F | 0.4" |
| Index | Johnstown | Colorado | National |
| Air quality index | 45 | 38 | 42 |
| Pollution index | 9,490,160 | 2,068,342 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 252 |
| Days with moderate air quality | 110 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.140% |
| Carbon Tetrachloride | 0.020% |
| Lead | 0.020% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Milliken, CO | 7,862 | 45 | 10.0% |
| Greeley, CO | 107,445 | 45 | 10.0% |
| Severance, CO | 5,611 | 45 | 10.0% |
| Platteville, CO | 3,017 | 45 | 10.0% |
| La Salle, CO | 3,377 | 45 | 10.0% |
| Johnstown, CO | 14,357 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Fort Campbell North, KY | 14,363 | 40 | 20.0% |
| Ozark, AL | 14,350 | 35 | 30.0% |
| Southern Pines, NC | 14,347 | 29 | 42.0% |
| Saint-Charles-Borromée, QC | 14,372 | n/a | |
| Lavaltrie, QC | 14,339 | n/a | |
| Johnstown, CO | 14,357 | 45 | 10.0% |
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