Overview
- The National Weather Service and the Illinois EPA issued the Air Pollution Action Day late Tuesday, May 26, and the alert remains in effect through Wednesday night.
- The warning covers McHenry, Lake, Kane, DuPage, Kendall, Grundy, Cook and Will counties in Illinois with a staggered alert starting at midnight for Lake, Porter, Newton and Jasper counties in northwest Indiana and LaPorte County beginning Wednesday morning.
- Officials say ozone is the main pollutant of concern and that it forms when sunlight triggers chemical reactions with vehicle and industrial emissions rather than from visible smoke.
- Public-health guidance urges older adults, children and people with lung or heart disease to limit prolonged outdoor activity and asks people with asthma to keep quick-relief medicine on hand.
- Forecasters expect ozone to peak in the afternoon when temperatures climb, so residents should monitor local AirNow updates and consider changing outdoor plans if conditions worsen.