St. Louis, Mo. – Heat is already radiating from sidewalks and parking lots across the St. Louis metro, and the most dangerous part of the day is still ahead. Air temperatures near 100 degrees combined with tropical humidity will create heat index values up to 115 degrees, making outdoor activities increasingly hazardous through the afternoon and early evening.
According to the National Weather Service in St. Louis, an Extreme Heat Warning remains in effect until 9 p.m. for the city of St. Louis, St. Louis County, St. Charles County, Jefferson County and neighboring communities in Missouri, along with Madison, St. Clair and Monroe counties in southwest Illinois. Officials warn that prolonged exposure to the heat can quickly lead to heat exhaustion or heat stroke without proper precautions.
Temperatures will climb to around 99 degrees this afternoon, while the combination of high humidity and light winds will push the heat index as high as 113 to 115 degrees. Anyone working outdoors or attending summer events should schedule frequent breaks, drink water often and seek air-conditioned spaces whenever possible.
Travelers using I-64, I-70, I-44, I-55, I-270 and the Poplar Street Bridge should prepare for dangerous conditions if vehicles become disabled. Keep bottled water in your vehicle, check tire pressure before longer trips and never leave children or pets inside parked cars, where interior temperatures can become deadly within minutes.
The intense heat begins easing Tuesday as highs fall to around 93 degrees, although the heat index may still approach 102 degrees during the afternoon. By Wednesday, a noticeably more comfortable air mass arrives with sunshine and highs near 88 degrees, offering the first meaningful break from the prolonged heat.
Late in the week, moisture gradually returns. A 20% chance of thunderstorms develops Thursday afternoon before shower and thunderstorm chances increase into Friday. While widespread severe weather is not expected at this time, isolated thunderstorms could produce brief heavy rain and lightning. Tornado potential currently appears low but will continue to be monitored as the next weather system approaches.
Looking into the 6-to-10-day outlook, temperatures are expected to trend above normal, although not as extreme as the current heat wave.
Five-Day Forecast for St. Louis, Missouri
- Today: Sunny and hot. High 99°F. Heat index up to 113–115°F.
- Tuesday: Mostly sunny. High 93°F. Heat index near 102°F.
- Wednesday: Sunny. High 88°F.
- Thursday: Sunny. High 90°F. Slight chance of afternoon thunderstorms.
- Friday: Partly sunny. High 84°F. Chance of showers and thunderstorms.
