St. Louis Weather Forecast: Upper 80s Heat Holds With Isolated Storm Risk in Illinois

ST. LOUIS, MISSOURI — The early October heatwave continues across Missouri and Illinois, with the National Weather Service (NWS) in St. Louis forecasting highs near 90 degrees today and isolated storm chances in parts of west-central Illinois.

Heat Continues Across the Region

Forecasters say much of the St. Louis metro area and surrounding communities will see highs in the mid-to-upper 80s, with plenty of sunshine dominating the afternoon. While October usually brings average highs in the low-to-mid 70s, today’s temperatures are running 10–15 degrees above normal, making it feel more like late summer than early fall.

Overnight lows are expected to remain mild, in the mid-60s to lower 70s, offering little relief from the unseasonable warmth.

Storm Chances in Illinois

The NWS noted a 20% chance of isolated showers and thunderstorms in west-central Illinois, particularly in counties bordering the Mississippi River. While rainfall totals are not expected to be widespread, any storms that develop could produce brief downpours, lightning, and gusty winds.

Communities such as Quincy, Jacksonville, and Pittsfield may see activity later in the afternoon or evening, though most areas will stay dry.

Extended Warmth Into Next Week

This hot pattern is not a one-day event. Forecasters say the region will continue experiencing above-normal heat through at least midweek, with highs expected to stay between 85 and 89 degrees into early next week.

Overnight lows will hold in the 60s to low 70s, maintaining a humid feel unusual for October.

Seasonal Context

Climatologists note that while warm spells in early fall are not unheard of, the persistence of upper 80s and near-90° days this late into the season is a growing trend across the Midwest.

October typically marks the arrival of crisp air and fall foliage season in Missouri and Illinois, but the current warmth may delay leaf color changes and impact agriculture, particularly for late-season crops such as soybeans and corn.

Safety and Outdoor Impacts

Officials advise residents to take precautions typically reserved for summer-like days:

• Stay hydrated if spending long hours outdoors.
• Limit strenuous activity during peak afternoon heat.
• Monitor local forecasts if traveling into Illinois, where isolated storms could pop up.

The dry conditions also mean an elevated risk of grass and brush fires, especially in rural areas where crops are being harvested.

Looking Ahead

The warm stretch is expected to hold into next week before a cold front brings cooler temperatures and rain chances later in the week. This system could provide some relief from the October heat and help return the region closer to seasonal averages.

Do you think St. Louis residents should prepare for more frequent October heatwaves as climate patterns shift, or is this just another temporary warm spell? Share your perspective and join the conversation at SaludaStandard-Sentinel.com.