| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 14°F | 30°F | 21°F | 3.1" |
| February | 13°F | 31°F | 21°F | 2.3" |
| March | 25°F | 44°F | 33°F | 2.5" |
| April | 40°F | 63°F | 50°F | 5.0" |
| May | 53°F | 74°F | 63°F | 6.8" |
| June | 61°F | 79°F | 70°F | 9.4" |
| July | 60°F | 80°F | 70°F | 4.8" |
| August | 57°F | 82°F | 69°F | 4.8" |
| September | 51°F | 78°F | 64°F | 4.8" |
| October | 44°F | 65°F | 53°F | 2.0" |
| November | 30°F | 46°F | 38°F | 5.8" |
| December | 26°F | 41°F | 33°F | 3.0" |
| Index | Matthews | Indiana | National |
| Air quality index | 35 | 56 | 42 |
| Pollution index | 508,399 | 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 | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Gas City, IN | 5,756 | 35 | 30.0% |
| Montpelier, IN | 1,790 | 35 | 30.0% |
| Yorktown, IN | 11,128 | 35 | 30.0% |
| Upland, IN | 3,701 | 35 | 30.0% |
| Gaston, IN | 860 | 35 | 30.0% |
| Matthews, IN | 475 | 35 | 30.0% |
| City | Population | Air Quality Index | National Avg. |
| Ualapue, HI | 475 | 15 | 70.0% |
| Diagonal, IA | 475 | 39 | 22.0% |
| Garden Valley, ID | 475 | 36 | 28.0% |
| Dayton, IL | 475 | 0 | 100.0% |
| Grantfork, IL | 475 | 54 | 8.0% |
| Matthews, IN | 475 | 35 | 30.0% |
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