| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | -4°F | 16°F | 6°F | 11.4" |
| February | -4°F | 17°F | 6°F | 3.4" |
| March | 12°F | 31°F | 21°F | 2.2" |
| April | 27°F | 51°F | 38°F | 1.3" |
| May | 38°F | 65°F | 51°F | 2.8" |
| June | 50°F | 74°F | 61°F | 4.0" |
| July | 53°F | 78°F | 65°F | 2.5" |
| August | 51°F | 78°F | 63°F | 2.6" |
| September | 44°F | 71°F | 56°F | 3.1" |
| October | 31°F | 54°F | 41°F | 0.8" |
| November | 17°F | 36°F | 25°F | 1.2" |
| December | -1°F | 17°F | 8°F | 7.7" |
| Index | Perth | North Dakota | National |
| Air quality index | 36 | 35 | 42 |
| Pollution index | 408,578 | 1,038,665 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 320 |
| Days with moderate air quality | 45 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Rocklake, ND | 114 | 36 | 28.0% |
| Mylo, ND | 31 | 36 | 28.0% |
| Belcourt, ND | 2,132 | 36 | 28.0% |
| Rolla, ND | 1,409 | 36 | 28.0% |
| Bisbee, ND | 73 | 36 | 28.0% |
| Perth, ND | 10 | 36 | 28.0% |
| City | Population | Air Quality Index | National Avg. |
| Memphis, AL | 10 | 35 | 30.0% |
| Indian Falls, CA | 10 | 46 | 8.0% |
| Bolan, IA | 10 | 15 | 70.0% |
| Hepburn, IA | 10 | 40 | 20.0% |
| Jacksonville, IA | 10 | 40 | 20.0% |
| Perth, ND | 10 | 36 | 28.0% |
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