Temperatures Saturday and Sunday reached the low 90's, but Sunday may have felt just a little more humid. That's because dew point temperatures were in the low to mid 60's versus the upper 50's they were at on Saturday.
Southerly winds will continue to pump moisture into northern Illinois and southern Wisconsin. This will keep dew point temperatures in the mid 60's, pushing heat index values into the middle to upper 90's through Wednesday.
It's not too often we experience this type of prolonged heat wave this early in the season. Since records began in Rockford in 1906, there have only been six other years where the high temperature reached 90 degrees, or higher, four consecutive days in a row before June 15th. The last time this occurred was back on June 6th-9th, 1963 - over half a century ago!! Temperatures in the 90's three days in a row are more common this early in June.