| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 11°F | 29°F | 20°F | 0.8" |
| February | 16°F | 35°F | 25°F | 0.4" |
| March | 26°F | 49°F | 37°F | 0.9" |
| April | 31°F | 60°F | 45°F | 1.1" |
| May | 38°F | 69°F | 54°F | 1.3" |
| June | 45°F | 80°F | 62°F | 0.9" |
| July | 50°F | 90°F | 70°F | 0.4" |
| August | 48°F | 88°F | 68°F | 0.6" |
| September | 41°F | 77°F | 59°F | 1.2" |
| October | 32°F | 61°F | 46°F | 1.3" |
| November | 24°F | 46°F | 34°F | 0.7" |
| December | 13°F | 31°F | 22°F | 0.8" |
| Index | Firth | Idaho | National |
| Air quality index | 27 | 32 | 42 |
| Pollution index | 3,578,590 | 2,063,710 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 344 |
| Days with moderate air quality | 21 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.030% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.030% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Shelley, ID | 4,455 | 27 | 46.0% |
| Moreland, ID | 1,246 | 27 | 46.0% |
| Ammon, ID | 16,403 | 27 | 46.0% |
| Basalt, ID | 436 | 27 | 46.0% |
| Riverside, ID | 1,131 | 27 | 46.0% |
| Firth, ID | 568 | 27 | 46.0% |
| City | Population | Air Quality Index | National Avg. |
| Dustin Acres, CA | 568 | 67 | 34.0% |
| Hopkinton, IA | 568 | 39 | 22.0% |
| Scranton, IA | 568 | 37 | 26.0% |
| Hutsonville, IL | 568 | 45 | 10.0% |
| Grayson, LA | 568 | 34 | 32.0% |
| Firth, ID | 568 | 27 | 46.0% |
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