| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 32°F | 23°F | 3.9" |
| February | 16°F | 34°F | 25°F | 2.5" |
| March | 30°F | 49°F | 38°F | 3.6" |
| April | 40°F | 64°F | 51°F | 5.7" |
| May | 51°F | 75°F | 62°F | 7.1" |
| June | 60°F | 83°F | 71°F | 7.2" |
| July | 63°F | 85°F | 74°F | 7.6" |
| August | 61°F | 83°F | 72°F | 7.2" |
| September | 53°F | 78°F | 65°F | 6.0" |
| October | 43°F | 65°F | 53°F | 4.0" |
| November | 31°F | 51°F | 40°F | 8.0" |
| December | 20°F | 36°F | 28°F | 4.2" |
| Index | Walnut | Illinois | National |
| Air quality index | 42 | 41 | 42 |
| Pollution index | 2,097,740 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 364 |
| Days with good air quality | 268 |
| Days with moderate air quality | 96 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.001% |
| Mercury | 0.300% |
| City | Population | Air Quality Index | National Avg. |
| Dover, IL | 141 | 0 | 100.0% |
| Ohio, IL | 509 | 0 | 100.0% |
| Wyanet, IL | 1,227 | 0 | 100.0% |
| Malden, IL | 411 | 0 | 100.0% |
| Amboy, IL | 2,453 | 0 | 100.0% |
| Walnut, IL | 1,340 | 42 | 16.0% |
| City | Population | Air Quality Index | National Avg. |
| Funny River, AK | 1,340 | 31 | 38.0% |
| Cleveland, AL | 1,340 | 43 | 14.0% |
| Saxapahaw, NC | 1,340 | 31 | 38.0% |
| Sandy, PA | 1,340 | 33 | 34.0% |
| Two Hills, AB | 1,340 | n/a | |
| Walnut, IL | 1,340 | 42 | 16.0% |
Here are the best places to live in Illinois
10 Best cities in Illinois for employment
These are the 10 most affordable cities in Illinois
Top 10 best public schools in Walnut