| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 36°F | 29°F | 6.9" |
| February | 19°F | 34°F | 26°F | 3.4" |
| March | 33°F | 54°F | 42°F | 3.3" |
| April | 41°F | 65°F | 52°F | 5.8" |
| May | 52°F | 78°F | 65°F | 3.4" |
| June | 63°F | 85°F | 74°F | 6.1" |
| July | 63°F | 83°F | 73°F | 5.8" |
| August | 65°F | 86°F | 75°F | 5.4" |
| September | 57°F | 83°F | 69°F | 7.0" |
| October | 46°F | 69°F | 57°F | 5.6" |
| November | 33°F | 53°F | 42°F | 7.3" |
| December | 21°F | 35°F | 27°F | 3.7" |
| Index | Garrett | Illinois | National |
| Air quality index | 42 | 41 | 50 |
| Pollution index | 703,218 | 3,347,295 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 281 |
| Days with moderate air quality | 84 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Arcola, IL | 2,881 | 42 | 16% |
| Tuscola, IL | 4,478 | 42 | 16% |
| Pesotum, IL | 514 | 42 | 16% |
| Atwood, IL | 1,106 | 42 | 16% |
| Villa Grove, IL | 2,222 | 42 | 16% |
| Garrett, IL | 79 | 42 | 16% |
| City, State | Population | Air Quality Index | National Avg. |
| Washington, CA | 79 | 44 | 12% |
| Fairburn, SD | 79 | 44 | 12% |
| Cayce, KY | 79 | 26 | 48% |
| Flute Springs, OK | 79 | 36 | 28% |
| Ozan, AR | 79 | 39 | 22% |
| Garrett, IL | 79 | 42 | 16% |
Here are the best places to live in Illinois
Top 10 cities in Illinois with the best education system
Check out the 10 safest cities in Illinois
10 Best cities in Illinois for employment