Humidity Levels in Illinois During September
The average humidity in September is listed below for places in Illinois. The tables give daily averages along with highest and lowest relative humidity levels.
Relative humidity measures the actual amount of moisture in the air as a percentage of the maximum amount of moisture the air can hold.
All the numbers here are averages for the years 1961 to 1990.
Average Humidity
In this table, the Daily number is the average of humidity readings taken every three hours throughout the day. Morning percentages are for 6 am and Afternoon measures are for 3 pm local standard time.
| Daily | Place | Morning | Afternoon |
|---|---|---|---|
| 71 | Chicago | 85 | 55 |
| 73 | Moline | 88 | 53 |
| 73 | Peoria | 88 | 54 |
| 74 | Rockford | 90 | 54 |
| 72 | Springfield | 88 | 52 |
Highest and Lowest Humidity
Below are the averages during September for maximum and minimum humidity levels in Illinois. The hours when this month's highest and lowest humidity readings usually occur are given in local standard time.
| High | Time | Place | Low | Time |
|---|---|---|---|---|
| 85.2 | 6 am | Chicago | 54.6 | 3 pm |
| 87.5 | 6 am | Moline | 53.4 | 3 pm |
| 87.9 | 6 am | Peoria | 54.0 | 3 pm |
| 89.8 | 6 am | Rockford | 54.2 | 3 pm |
| 88.4 | 6 am | Springfield | 51.9 | 3 pm |
Reference
World Data Center for Meteorology. Climate of the World.