Peoria, Ill. (WMBD) — Central Illinois is expected to experience some of the coolest air since late April as temperatures are likely to drop into the mid to upper 30s. The National Weather Service has issued a Frost Advisory for much of Central Illinois from 12 am to 8 am Wednesday.

As high pressure builds across Central Illinois skies will remain clear and winds will become light. With temperatures dropping into the mid to upper 30s, areas of frost are expected to develop by early Wednesday morning. The most widespread frost is expected west of the Illinois River where temperatures are more likely to drop to or below 36°. Further east, frost will remain a bit more patchy.

Frost could damage or kill sensitive vegetation if left uncovered, so be sure to throw a light blanket over plants that could be susceptible to the colder temperatures.

Why does frost form?

Frost forms when temperatures drop into the mid to upper 30s with clear skies and light winds. Even though air temperatures could be a few degrees above freezing, the temperature of the air right off the ground is cooler. As long as dew point temperatures are at or just below freezing, frost can form as radiational cooling causes temperatures to drop to the dew point. Once the dew point is reached, dew develops on the grass and freezes as the temperature just above the ground are at or below freezing.