* WHAT...FOR THE DENSE FOG ADVISORY, VISIBILITY REDUCED TO ONEQUARTER MILE IN DENSE FOG. FOR THE FIRST HEAT ADVISORY, HEAT INDEX VALUES 100 TO 105 EXPECTED. FOR THE SECOND HEAT ADVISORY, HEAT INDEX VALUES 105 TO 110 EXPECTED.

* WHERE...MASON, MENARD, SANGAMON, AND TAZEWELL COUNTIES.

* WHEN...FOR THE DENSE FOG ADVISORY, UNTIL 8 AM CDT THIS MORNING. FOR THE FIRST HEAT ADVISORY, FROM 1 PM THIS AFTERNOON TO 7 PM CDT THIS EVENING. FOR THE SECOND HEAT ADVISORY, FROM 11 AM MONDAY TO MIDNIGHT CDT THURSDAY NIGHT.

* IMPACTS...HOT TEMPERATURES AND HIGH HUMIDITY MAY CAUSE HEAT ILLNESSES. LOW VISIBILITY COULD MAKE DRIVING CONDITIONS HAZARDOUS.