| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 2°F | 21°F | 12°F | 1.0" |
| February | 4°F | 23°F | 13°F | 0.8" |
| March | 15°F | 36°F | 24°F | 1.9" |
| April | 26°F | 50°F | 37°F | 2.2" |
| May | 39°F | 67°F | 53°F | 6.2" |
| June | 50°F | 76°F | 63°F | 8.2" |
| July | 55°F | 79°F | 66°F | 3.4" |
| August | 52°F | 81°F | 65°F | 2.0" |
| September | 46°F | 72°F | 57°F | 4.5" |
| October | 32°F | 55°F | 42°F | 3.4" |
| November | 17°F | 37°F | 26°F | 1.3" |
| December | 3°F | 21°F | 12°F | 0.5" |
| Index | Portal | North Dakota | National |
| Air quality index | 34 | 35 | 42 |
| Pollution index | 173,888 | 1,038,665 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 309 |
| Days with moderate air quality | 53 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| 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. |
| Larson, ND | 0 | 34 | 32.0% |
| Bowbells, ND | 299 | 34 | 32.0% |
| Lignite, ND | 157 | 34 | 32.0% |
| Columbus, ND | 74 | 34 | 32.0% |
| Flaxton, ND | 112 | 34 | 32.0% |
| Portal, ND | 132 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Yellow Bluff, AL | 132 | 52 | 4.0% |
| Vallecito, CA | 132 | 39 | 22.0% |
| Otter Creek, FL | 132 | 35 | 30.0% |
| Blockton, IA | 132 | 43 | 14.0% |
| Geneva, IA | 132 | 15 | 70.0% |
| Portal, ND | 132 | 34 | 32.0% |
Here are the best places to live in North Dakota
Check out the 10 safest cities in North Dakota
These are the 10 cheapest cities in North Dakota
See the best places to live in Portal