| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 35°F | 26°F | 5.9" |
| February | 21°F | 40°F | 30°F | 2.5" |
| March | 33°F | 54°F | 42°F | 5.0" |
| April | 42°F | 66°F | 53°F | 8.5" |
| May | 53°F | 76°F | 64°F | 7.3" |
| June | 62°F | 83°F | 72°F | 10.2" |
| July | 63°F | 85°F | 74°F | 6.2" |
| August | 60°F | 83°F | 71°F | 6.0" |
| September | 54°F | 78°F | 65°F | 9.2" |
| October | 43°F | 66°F | 53°F | 4.4" |
| November | 33°F | 53°F | 42°F | 6.4" |
| December | 25°F | 40°F | 32°F | 4.8" |
| Index | Westfield | Indiana | National |
| Air quality index | 54 | 56 | 42 |
| Pollution index | 680,492 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 148 |
| Days with moderate air quality | 212 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Arcadia, IN | 1,530 | 42 | 16.0% |
| Atlanta, IN | 859 | 42 | 16.0% |
| Cicero, IN | 4,921 | 42 | 16.0% |
| Kirklin, IN | 1,125 | 42 | 16.0% |
| Noblesville, IN | 64,430 | 42 | 16.0% |
| Westfield, IN | 41,652 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| La Quinta, CA | 41,650 | 89 | 78.0% |
| Oakley, CA | 41,656 | 45 | 10.0% |
| Mableton, GA | 41,647 | 52 | 4.0% |
| Huntsville, TX | 41,664 | 52 | 4.0% |
| Puyallup, WA | 41,666 | 30 | 40.0% |
| Westfield, IN | 41,652 | 54 | 8.0% |
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