The St. Louis County Office of Emergency Management and the National Weather Service in St. Louis have issued a heat advisory in effect from 1 p.m. to 8 p.m. Monday.

Heat index values may reach up to 105 degrees due to temperatures in the low 90s, with dewpoints in the mid 70s.

Dangerously high temperatures and humidity can quickly cause heat stress or heat stroke if precautions are not taken. The very young, the elderly, those without air conditioning and those participating in strenuous outdoor activities will be the most susceptible. Car interiors can reach lethal temperatures in a matter of minutes.

The advisory affects St. Louis County and St. Louis city, along with St. Charles County in Missouri and St. Clair and Madison counties in Illinois.

People are advised to avoid poorly ventilated areas and prolonged work in the sun. Keep plenty of liquids on hand and try to stay in an air conditioned environment. Wear light weight and loose fitting clothing when possible and drink plenty of water.

Young children and pets should never be left unattended in vehicles under any circumstances.

People in the St. Louis metropolitan area can get more information about cooling centers or energy assistance related to the excessive heat by calling the United Way of Greater St. Louis at 800-427-4626, or if calling from a land line phone dial 2-1-1. You can also call Cool Down St. Louis at 314-241-7668.