| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 36°F | 27°F | 2.6" |
| February | 20°F | 39°F | 29°F | 2.0" |
| March | 32°F | 53°F | 42°F | 2.7" |
| April | 42°F | 66°F | 53°F | 4.3" |
| May | 51°F | 75°F | 63°F | 4.4" |
| June | 61°F | 84°F | 72°F | 5.8" |
| July | 64°F | 85°F | 74°F | 4.8" |
| August | 62°F | 85°F | 73°F | 3.6" |
| September | 55°F | 79°F | 66°F | 3.2" |
| October | 44°F | 67°F | 55°F | 3.3" |
| November | 33°F | 53°F | 43°F | 3.1" |
| December | 24°F | 40°F | 31°F | 3.1" |
| Index | Darlington | Indiana | National |
| Air quality index | 52 | 56 | 50 |
| Pollution index | 1,601,640 | 3,773,618 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 170 |
| Days with moderate air quality | 195 |
| Days w/ poor A.Q. for sensitive groups | |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.004% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.040% |
| Mercury | 0.290% |
| City, State | Population | Air Quality Index | National Avg. |
| Clarks Hill, IN | 635 | 52 | 4% |
| New Market, IN | 494 | 52 | 4% |
| Thorntown, IN | 1,637 | 52 | 4% |
| Colfax, IN | 781 | 52 | 4% |
| Ladoga, IN | 1,150 | 52 | 4% |
| Darlington, IN | 780 | 52 | 4% |
| City, State | Population | Air Quality Index | National Avg. |
| Wilbur, WA | 780 | 24 | 52% |
| Greensburg, LA | 780 | 28 | 44% |
| Lincoln, MT | 780 | 35 | 30% |
| South Coffeyville, OK | 780 | 37 | 26% |
| Arco, ID | 780 | 35 | 30% |
| Darlington, IN | 780 | 52 | 4% |