| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 24°F | 35°F | 29°F | 4.1" |
| February | 26°F | 40°F | 32°F | 2.4" |
| March | 31°F | 49°F | 39°F | 3.4" |
| April | 36°F | 58°F | 45°F | 2.8" |
| May | 43°F | 69°F | 55°F | 2.9" |
| June | 50°F | 75°F | 61°F | 6.5" |
| July | 55°F | 87°F | 70°F | 3.1" |
| August | 54°F | 86°F | 69°F | 3.1" |
| September | 47°F | 76°F | 60°F | 2.9" |
| October | 38°F | 59°F | 47°F | 4.0" |
| November | 31°F | 44°F | 37°F | 3.4" |
| December | 23°F | 34°F | 28°F | 3.9" |
| Index | Heron | Montana | National |
| Air quality index | 43 | 34 | 42 |
| Pollution index | 4,670,990 | 834,473 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 252 |
| Days with moderate air quality | 111 |
| Days w/ poor A.Q. for sensitive groups | 2 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.050% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.060% |
| Mercury | 0.003% |
| City | Population | Air Quality Index | National Avg. |
| Noxon, MT | 162 | 37 | 26.0% |
| Hope, ID | 97 | 43 | 14.0% |
| Clark Fork, ID | 849 | 43 | 14.0% |
| East Hope, ID | 168 | 43 | 14.0% |
| Heron, MT | 281 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Copper Center, AK | 281 | 31 | 38.0% |
| Madrid, AL | 281 | 35 | 30.0% |
| Carl, GA | 281 | 37 | 26.0% |
| Jewett, IL | 281 | 40 | 20.0% |
| Lisbon, IL | 281 | 0 | 100.0% |
| Heron, MT | 281 | 43 | 14.0% |
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