| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 36°F | 26°F | 0.9" |
| February | 20°F | 37°F | 28°F | 0.8" |
| March | 26°F | 44°F | 34°F | 2.4" |
| April | 31°F | 50°F | 40°F | 1.8" |
| May | 37°F | 59°F | 47°F | 2.4" |
| June | 49°F | 73°F | 61°F | 2.8" |
| July | 53°F | 75°F | 63°F | 2.1" |
| August | 51°F | 72°F | 60°F | 2.5" |
| September | 44°F | 67°F | 54°F | 2.2" |
| October | 36°F | 56°F | 45°F | 3.3" |
| November | 28°F | 46°F | 35°F | 0.6" |
| December | 19°F | 36°F | 27°F | 1.2" |
| Index | Portland | Colorado | National |
| Air quality index | 44 | 38 | 42 |
| Pollution index | 262,465 | 2,068,342 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 276 |
| Days with moderate air quality | 89 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.003% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Loghill Village, CO | 707 | 44 | 12.0% |
| Mountain Village, CO | 1,776 | 44 | 12.0% |
| Ridgway, CO | 1,142 | 44 | 12.0% |
| Telluride, CO | 2,059 | 44 | 12.0% |
| Ouray, CO | 1,046 | 44 | 12.0% |
| Portland, CO | 126 | 44 | 12.0% |
| City | Population | Air Quality Index | National Avg. |
| Venetie, AK | 126 | 38 | 24.0% |
| Toxey, AL | 126 | 36 | 28.0% |
| Gu Oidak, AZ | 126 | 47 | 6.0% |
| Myers Flat, CA | 126 | 27 | 46.0% |
| Lincoln, IA | 126 | 39 | 22.0% |
| Portland, CO | 126 | 44 | 12.0% |
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