| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 33°F | 22°F | 0.3" |
| February | 17°F | 40°F | 27°F | 0.3" |
| March | 26°F | 52°F | 38°F | 0.8" |
| April | 33°F | 61°F | 46°F | 1.2" |
| May | 41°F | 71°F | 56°F | 1.3" |
| June | 50°F | 83°F | 66°F | 0.2" |
| July | 60°F | 92°F | 76°F | 0.0" |
| August | 54°F | 85°F | 69°F | 0.5" |
| September | 44°F | 72°F | 57°F | 1.1" |
| October | 34°F | 57°F | 44°F | 1.8" |
| November | 24°F | 48°F | 34°F | 0.4" |
| December | 10°F | 31°F | 19°F | 0.3" |
| Index | Johnstown | Wyoming | National |
| Air quality index | 45 | 39 | 42 |
| Pollution index | 270,167 | 1,779,975 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 294 |
| Days with moderate air quality | 69 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.002% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Arapahoe, WY | 1,701 | 45 | 10.0% |
| Hudson, WY | 417 | 45 | 10.0% |
| Boulder Flats, WY | 342 | 45 | 10.0% |
| Ethete, WY | 1,644 | 45 | 10.0% |
| Pavillion, WY | 433 | 45 | 10.0% |
| Johnstown, WY | 221 | 45 | 10.0% |
| City | Population | Air Quality Index | National Avg. |
| Newbern, AL | 221 | 35 | 30.0% |
| Widener, AR | 221 | 45 | 10.0% |
| Jeddito, AZ | 221 | 17 | 66.0% |
| Conroy, IA | 221 | 39 | 22.0% |
| Moorhead, IA | 221 | 40 | 20.0% |
| Johnstown, WY | 221 | 45 | 10.0% |
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