| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 35°F | 57°F | 45°F | 8.2" |
| February | 39°F | 60°F | 48°F | 6.0" |
| March | 46°F | 69°F | 57°F | 8.6" |
| April | 55°F | 78°F | 65°F | 9.5" |
| May | 61°F | 83°F | 71°F | 7.5" |
| June | 70°F | 91°F | 80°F | 7.6" |
| July | 73°F | 93°F | 82°F | 6.7" |
| August | 72°F | 93°F | 81°F | 7.3" |
| September | 65°F | 89°F | 76°F | 3.5" |
| October | 54°F | 79°F | 65°F | 7.4" |
| November | 44°F | 66°F | 54°F | 6.8" |
| December | 39°F | 58°F | 47°F | 7.8" |
| Index | Portland | Arkansas | National |
| Air quality index | 43 | 38 | 42 |
| Pollution index | 519,038 | 1,487,822 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 270 |
| Days with moderate air quality | 94 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Parkdale, AR | 269 | 34 | 32.0% |
| Wilmot, AR | 499 | 34 | 32.0% |
| Montrose, AR | 402 | 43 | 14.0% |
| Eudora, AR | 2,246 | 43 | 14.0% |
| Jerome, AR | 42 | 43 | 14.0% |
| Portland, AR | 375 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Wabbaseka, AR | 375 | 45 | 10.0% |
| Steamboat, AZ | 375 | 17 | 66.0% |
| Rollinsville, CO | 375 | 47 | 6.0% |
| Braswell, GA | 375 | 44 | 12.0% |
| Lomax, IL | 375 | 29 | 42.0% |
| Portland, AR | 375 | 43 | 14.0% |
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