Weather
St. Louis, MO Frost Advisory Expanded Early Sunday, Oct. 18
St. Louis, MO – An expanded Frost Advisory is affecting more communities across eastern Missouri and west central Illinois early Sunday, Oct. 18, as chilly overnight conditions increase the potential
By Natalie Rhodes · 2026-10-18T09:02:26.880Z
St. Louis, MO – An expanded Frost Advisory is affecting more communities across eastern Missouri and west central Illinois early Sunday, Oct. 18, as chilly overnight conditions increase the potential for frost and damage to sensitive outdoor vegetation.
According to the National Weather Service in St. Louis, the advisory was expanded late Saturday evening to include additional portions of both states ahead of Sunday morning's coldest temperatures.
The updated advisory map, issued at 10:40 p.m. Saturday, Oct. 17, shows widespread coverage across the greater St. Louis region and surrounding communities.
Which Illinois and Missouri communities are affected?
The expanded advisory area includes portions of west central and southern Illinois, with communities around Springfield, Carlinville, Vandalia, Salem, Nashville and Chester appearing within the highlighted region.
Across Missouri, the advisory extends through portions of the St. Louis metropolitan area and surrounding communities, including areas near Troy, Hermann, Jefferson City, Farmington and Cape Girardeau.
The map also highlights additional counties across eastern and central Missouri, although advisory coverage varies by location.
Residents should check their specific county's advisory status through the National Weather Service.
Why is frost a concern Sunday morning?
Frost can develop when exposed surfaces cool enough for ice crystals to form, potentially damaging sensitive plants even when standard air temperatures remain above freezing.
Flowers, vegetables, potted plants and other vulnerable vegetation may be affected.
The National Weather Service specifically recommends covering outdoor vegetation and bringing potted plants indoors to reduce the risk of damage.
What happens after Sunday morning?
The supplied advisory update focuses on the early Sunday morning frost threat and does not provide a specific expiration time.
Residents should monitor updated National Weather Service alerts to determine when the advisory ends.
Looking ahead: NOAA's Oct. 25–31 outlook favors above normal temperatures across much of Illinois and Missouri, suggesting a potentially milder pattern heading toward Halloween.
For now, the immediate concern remains the expanded Sunday morning frost advisory and protecting sensitive plants from the cold.