| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 17°F | 34°F | 25°F | 0.6" |
| February | 22°F | 42°F | 32°F | 0.6" |
| March | 26°F | 52°F | 38°F | 0.9" |
| April | 29°F | 59°F | 44°F | 0.8" |
| May | 36°F | 69°F | 52°F | 1.6" |
| June | 42°F | 76°F | 59°F | 1.4" |
| July | 47°F | 88°F | 68°F | 0.5" |
| August | 44°F | 88°F | 66°F | 0.5" |
| September | 37°F | 78°F | 57°F | 0.4" |
| October | 30°F | 62°F | 45°F | 0.8" |
| November | 24°F | 46°F | 34°F | 0.7" |
| December | 16°F | 34°F | 25°F | 1.0" |
| Index | Halfway | Oregon | National |
| Air quality index | 20 | 32 | 42 |
| Pollution index | 1,082,340 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 344 |
| Days with moderate air quality | 21 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Richland, OR | 245 | 20 | 60.0% |
| Halfway, OR | 303 | 20 | 60.0% |
| City | Population | Air Quality Index | National Avg. |
| Twain, CA | 303 | 46 | 8.0% |
| Surrency, GA | 303 | 26 | 48.0% |
| Bagley, IA | 303 | 37 | 26.0% |
| Bush, IL | 303 | 43 | 14.0% |
| Opdyke, IL | 303 | 43 | 14.0% |
| Halfway, OR | 303 | 20 | 60.0% |
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