| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 32°F | 23°F | 1.5" |
| February | 16°F | 34°F | 24°F | 1.4" |
| March | 29°F | 49°F | 38°F | 2.3" |
| April | 39°F | 62°F | 50°F | 3.9" |
| May | 49°F | 73°F | 61°F | 4.3" |
| June | 59°F | 82°F | 70°F | 4.5" |
| July | 62°F | 84°F | 73°F | 4.3" |
| August | 60°F | 82°F | 71°F | 4.3" |
| September | 53°F | 77°F | 64°F | 2.9" |
| October | 42°F | 64°F | 52°F | 3.6" |
| November | 30°F | 50°F | 40°F | 2.1" |
| December | 20°F | 36°F | 28°F | 2.2" |
| Index | Plano | Illinois | National |
| Air quality index | 0 | 41 | 42 |
| Pollution index | 1,874,490 | 3,148,694 | 2,726,193 |
| Measurement | Total |
| Days measured | 335 |
| Days with good air quality | 334 |
| Days with moderate air quality | 1 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.002% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.010% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Sheridan, IL | 2,829 | 0 | 100.0% |
| Millington, IL | 662 | 0 | 100.0% |
| Montgomery, IL | 19,515 | 0 | 100.0% |
| Plattville, IL | 190 | 0 | 100.0% |
| Big Rock, IL | 1,271 | 0 | 100.0% |
| Plano, IL | 11,058 | 0 | 100.0% |
| City | Population | Air Quality Index | National Avg. |
| Lanham, MD | 11,054 | 47 | 6.0% |
| Holbrook, MA | 11,051 | 43 | 14.0% |
| Ocean City, NJ | 11,065 | 37 | 26.0% |
| Marieville, QC | 11,065 | n/a | |
| La Homa, TX | 11,066 | 42 | 16.0% |
| Plano, IL | 11,058 | 0 | 100.0% |
Here are the best places to live in Illinois
10 best cities to buy a new house in Illinois
Top 10 cities in Illinois with the best education system
Top 10 best public schools in Plano