FirstWarn Weather

First Warn Forecast: Sunday, July 19, 2026
Hot, Humid Weather Continues Today
Scattered Thunderstorms Could Produce Heavy Rain and Gusty Winds
Relief Finally Arrives by Midweek

Another hot and humid day is on tap across much of the Mid-Mississippi Valley, but not everyone will experience the same weather. A stalled cold front stretching across the region will create a sharp contrast in temperatures while also serving as the focus for scattered to numerous showers and thunderstorms this afternoon and evening.

For much of central and southeastern Missouri, the St. Louis metro, and southwestern Illinois, expect a warm, muggy day with temperatures climbing to around 90 degrees. Combined with high humidity, it will feel closer to 100 degrees during the afternoon before thunderstorms begin to develop. If you have outdoor plans, be prepared for rapidly changing weather and make sure you have a way to receive weather alerts.

Scattered showers and thunderstorms will become more numerous from late morning through the evening, especially along and south of the Interstate 70 corridor. While widespread severe weather is not expected, a few stronger storms could produce wind gusts of 40 to 60 mph, frequent lightning, and torrential rainfall capable of causing brief localized flooding. The atmosphere contains abundant moisture, so any storm that develops will be capable of producing heavy rain in a short amount of time. Fortunately, storms will remain scattered, meaning many locations will also experience long periods of dry weather.

Farther north across northeastern Missouri and portions of west-central and south-central Illinois, today will feel noticeably different. Temperatures will remain in the middle 80s behind the stalled front, providing a welcome break from the recent stretch of oppressive heat. However, that cooler air comes with another concern as smoke from Canadian wildfires is expected to drift into the area during the afternoon and evening.

The wildfire smoke is expected to reduce air quality across northern sections of the viewing area, particularly for individuals with asthma, COPD, heart disease, or other respiratory conditions. Some areas may also notice hazy skies and slightly reduced visibility. If you're sensitive to poor air quality, consider limiting prolonged outdoor activity, especially during the afternoon.

Tonight, any lingering showers will gradually diminish, but areas that receive heavier rainfall could wake up to patches of fog Monday morning. The combination of wet ground, light winds, and lingering humidity will provide favorable conditions for locally dense fog before sunrise.

Monday brings another surge of heat and humidity as the stalled front lifts back north as a warm front. Afternoon highs will once again reach the lower to middle 90s across much of Missouri, with heat index values climbing between 100 and 105 degrees. A few isolated to scattered afternoon thunderstorms are possible once again, although many communities will remain dry for most of the day.

The biggest change arrives Tuesday as a stronger cold front sweeps through the region. While there will be another opportunity for showers and thunderstorms, there is also the potential for a few stronger storms capable of producing damaging wind gusts if enough instability develops ahead of the front. We'll continue to monitor that threat over the next couple of days as confidence increases.

By Wednesday, the weather finally takes a turn in a much more comfortable direction. High temperatures will fall back into the 80s, humidity levels will drop significantly, and dew points will return to the 50s and lower 60s. The result will be a refreshing stretch of summer weather with sunshine, lower humidity, and dry conditions expected through at least the middle of the week.

What You Need to Know
Hot and humid conditions continue today across much of Missouri and southwestern Illinois, with heat index values near 100 degrees.
Scattered showers and thunderstorms this afternoon and evening could produce gusty winds, dangerous lightning, and localized heavy rainfall.
Northeastern Missouri and parts of west-central Illinois will be cooler today but may experience reduced air quality from Canadian wildfire smoke.
Monday turns hot again with heat index values reaching 100 to 105 degrees.
A cold front Tuesday brings the chance for additional thunderstorms before cooler, drier air arrives Wednesday.

First. Accurate. Trusted. That's your First Warn Forecast. Enjoy the break from the heat if you're north of the front today, but everyone should remain weather aware this afternoon as scattered thunderstorms develop. Better weather is finally on the horizon by the middle of the week.

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Debbie Wehmeyer, Karen Kuhl, Margie John Flieg, Terri Hoff, Brenda Lightfoot, Shane Thompson, Mindy House, Brenda Schweigert, Jeanne Mattingly, Patty Weisbrod

First Warn Forecast
Monday, July 13, 2026
Summer heat gradually returns with temperatures climbing back into the 90s.
Most of the region stays dry, with only isolated storm chances across southern Missouri and southern Illinois.
Heat and humidity build through the week, with heat index values nearing 100 to 105 degrees by Thursday through Saturday.

After a pleasant weekend by mid-July standards, the familiar summer heat begins to make a comeback this week. High pressure building across the Midwest will dominate our weather pattern, bringing several days of dry conditions, plenty of sunshine, and a gradual warming trend. While today's temperatures will top out in the middle to upper 80s with humidity remaining relatively manageable, each day will become a little warmer and a little more humid as we move toward the weekend.

The good news is that most communities will stay dry through much of the week. The only exception will be across portions of southeast Missouri and southwest Illinois, where a few isolated showers or thunderstorms could develop during the middle of the week. Even there, many locations will remain rain-free, and widespread rainfall is not expected. For most of the region, outdoor plans should go uninterrupted by the weather.

By Wednesday, temperatures will climb into the lower 90s, and humidity levels will begin increasing as moisture returns from the Gulf. While it won't be the extreme heat we experienced a couple of weeks ago, it will certainly feel much more like a typical Missouri and Illinois summer. Afternoon heat index values will approach 100 degrees in some locations by Wednesday before climbing into the 100 to 105-degree range Thursday through Saturday. If current trends continue, portions of the region could once again approach Heat Advisory criteria by the end of the week.

Although this upcoming stretch won't likely rival the historic heat waves seen across the northern Plains and Upper Midwest, where record temperatures are possible, it will still be important to take precautions if you're spending extended time outdoors. Stay hydrated, take frequent breaks in the shade or air conditioning, and never leave children or pets inside a parked vehicle, even for a few minutes. Heat-related illnesses can develop quickly during prolonged exposure to high temperatures and humidity.

Looking ahead, the overall weather pattern remains relatively quiet. Temperatures stay in the 90s through the weekend with only limited opportunities for rainfall. While a few isolated storms are possible from time to time, especially across our southern counties, widespread relief from the heat does not appear likely anytime soon. Summer has settled back in, and it looks like it's here to stay for a while.