| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 33°F | 25°F | 1.6" |
| February | 19°F | 35°F | 26°F | 1.4" |
| March | 30°F | 49°F | 39°F | 2.0" |
| April | 40°F | 62°F | 50°F | 3.3" |
| May | 50°F | 73°F | 61°F | 3.4" |
| June | 60°F | 82°F | 70°F | 3.9" |
| July | 63°F | 84°F | 73°F | 4.0" |
| August | 61°F | 82°F | 71°F | 4.9" |
| September | 55°F | 77°F | 65°F | 2.4" |
| October | 44°F | 64°F | 53°F | 3.6" |
| November | 33°F | 51°F | 41°F | 2.1" |
| December | 23°F | 37°F | 30°F | 1.8" |
| Index | Winfield | Indiana | National |
| Air quality index | 37 | 56 | 42 |
| Pollution index | 898,555 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 305 |
| Days with moderate air quality | 55 |
| Days w/ poor A.Q. for sensitive groups | 4 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.005% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Merrillville, IN | 34,871 | 37 | 26.0% |
| De Motte, IN | 4,093 | 37 | 26.0% |
| Chesterton, IN | 13,884 | 37 | 26.0% |
| Lakes of the Four Seasons, IN | 7,081 | 37 | 26.0% |
| Salt Creek Commons, IN | 1,941 | 37 | 26.0% |
| Winfield, IN | 5,879 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Clearfield, PA | 5,878 | 33 | 34.0% |
| Country Homes, WA | 5,877 | 43 | 14.0% |
| Glendale, MO | 5,881 | 54 | 8.0% |
| Paulsboro, NJ | 5,881 | 51 | 2.0% |
| International Falls, MN | 5,876 | 35 | 30.0% |
| Winfield, IN | 5,879 | 37 | 26.0% |
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