| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 37°F | 29°F | 8.1" |
| February | 18°F | 34°F | 26°F | 4.1" |
| March | 32°F | 52°F | 41°F | 5.7" |
| April | 40°F | 64°F | 51°F | 7.1" |
| May | 51°F | 75°F | 63°F | 2.9" |
| June | 62°F | 84°F | 73°F | 4.0" |
| July | 61°F | 84°F | 72°F | 4.9" |
| August | 64°F | 85°F | 74°F | 8.8" |
| September | 57°F | 81°F | 68°F | 4.3" |
| October | 49°F | 68°F | 58°F | 5.4" |
| November | 34°F | 53°F | 43°F | 6.2" |
| December | 22°F | 36°F | 29°F | 5.0" |
| Index | Portland | Indiana | National |
| Air quality index | 35 | 56 | 42 |
| Pollution index | 1,533,570 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 352 |
| Days with good air quality | 319 |
| Days with moderate air quality | 33 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.003% |
| Mercury | 0.001% |
| City | Population | Air Quality Index | National Avg. |
| Geneva, IN | 1,227 | 31 | 38.0% |
| Bryant, IN | 214 | 35 | 30.0% |
| Redkey, IN | 1,493 | 35 | 30.0% |
| Albany, IN | 2,365 | 35 | 30.0% |
| Dunkirk, IN | 1,923 | 35 | 30.0% |
| Portland, IN | 5,972 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Highland Lakes, AL | 5,973 | 53 | 6.0% |
| Minot AFB, ND | 5,974 | 34 | 32.0% |
| Ocean City, FL | 5,969 | 31 | 38.0% |
| Salton City, CA | 5,975 | 58 | 16.0% |
| Northville, MI | 5,968 | 40 | 20.0% |
| Portland, IN | 5,972 | 35 | 30.0% |
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