| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 35°F | 29°F | 7.9" |
| February | 18°F | 32°F | 25°F | 3.3" |
| March | 33°F | 51°F | 42°F | 4.8" |
| April | 42°F | 63°F | 53°F | 4.5" |
| May | 54°F | 75°F | 67°F | 4.0" |
| June | 65°F | 83°F | 75°F | 7.3" |
| July | 65°F | 83°F | 76°F | 6.5" |
| August | 66°F | 84°F | 77°F | 8.2" |
| September | 59°F | 81°F | 71°F | 11.9" |
| October | 49°F | 67°F | 59°F | 4.4" |
| November | 35°F | 51°F | 43°F | 7.4" |
| December | 23°F | 34°F | 29°F | 4.1" |
| Index | Royal Center | Indiana | National |
| Air quality index | 37 | 56 | 42 |
| Pollution index | 2,150,900 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 351 |
| Days with good air quality | 319 |
| Days with moderate air quality | 32 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.650% |
| Mercury | 1.040% |
| City | Population | Air Quality Index | National Avg. |
| Logansport, IN | 18,342 | 37 | 26.0% |
| Kewanna, IN | 451 | 37 | 26.0% |
| Star City, IN | 286 | 37 | 26.0% |
| Winamac, IN | 2,736 | 37 | 26.0% |
| Walton, IN | 937 | 37 | 26.0% |
| Royal Center, IN | 922 | 37 | 26.0% |
| City | Population | Air Quality Index | National Avg. |
| Stephenson, MI | 922 | 36 | 28.0% |
| Cass Lake, MN | 922 | 29 | 42.0% |
| Walhalla, ND | 922 | 33 | 34.0% |
| Norfolk, NY | 922 | 0 | 100.0% |
| Morgandale, OH | 922 | 42 | 16.0% |
| Royal Center, IN | 922 | 37 | 26.0% |