FirstWarn Weather

First Warn Forecast: Monday, July 20, 2026
Dangerous Heat Builds Across the Region
Storm Chances Increase Tonight North of I-70
Cooler, Drier Weather Arrives Wednesday

Hot and humid conditions will take over much of the region today, with afternoon heat index values climbing between 100 and 108 degrees. The heat will continue Tuesday, especially along and south of Interstate 70, before a strong cold front finally brings much cooler and less humid weather by Wednesday.

Areas of fog developed early this morning, particularly near the Mississippi River and in locations that received rain on Sunday. Canadian wildfire smoke may also be contributing to reduced visibility across portions of Illinois. A few locations could briefly experience visibility near one-quarter mile, but the fog should quickly improve after sunrise. Wildfire smoke may linger across west-central and south-central Illinois through much of the day, continuing to reduce air quality even after visibility improves.

Temperatures this afternoon will climb into the lower and middle 90s across much of the area. Combined with high humidity, it will feel more like 100 to 108 degrees in the Heat Advisory area. Anyone spending time outdoors should drink plenty of water, limit strenuous activity during the hottest part of the afternoon, and take frequent breaks in air conditioning. Children and pets should never be left inside a parked vehicle, even for a few minutes.

Most locations will remain dry today, although an isolated afternoon shower or thunderstorm could develop across southeastern Missouri. Storm coverage will be much lower than what many locations experienced Sunday, and widespread rainfall is not expected during the daytime hours.

The better opportunity for showers and thunderstorms arrives overnight tonight into Tuesday morning, primarily north of Interstate 70. Storms are expected to develop across Iowa and Wisconsin before moving south or southeast toward northeastern Missouri and west-central Illinois. There is still uncertainty regarding how far south the storms will travel, so some locations may miss the activity entirely.

Should storms reach the northern portion of the area, a few could become strong to marginally severe. The main concerns would be damaging wind gusts, isolated hail, frequent lightning, and locally heavy rainfall. The atmosphere will contain enough moisture for thunderstorms to produce heavy rain in a short amount of time, particularly along the southwestern edge of any organized storm complex. This threat remains conditional and will depend heavily on how storms develop farther north this evening.

A cold front will slowly move south through the region Tuesday. Areas along and south of Interstate 70 will remain hot and humid ahead of the front, with highs in the 90s and heat index values between 100 and 108 degrees. A few locations could briefly approach 110 degrees. Farther north, temperatures may still reach near 90, but falling humidity behind the front will make conditions feel noticeably less oppressive.

Additional showers and thunderstorms may develop along the front Tuesday afternoon or evening, but coverage remains uncertain. The strongest atmospheric support will pass northeast of the region, and a layer of warmer air above the surface may limit storm development locally. We will continue monitoring the possibility of storms as the front crosses the area.

The long-awaited change arrives Wednesday as a much cooler and drier air mass settles across the Mid-Mississippi Valley. Afternoon temperatures will remain in the 80s, while dew points fall into the 50s and lower 60s. The lower humidity will make conditions feel considerably more comfortable after several days of dangerous summer heat.

Dry weather is expected Wednesday and Thursday under an area of high pressure. Chances for showers and thunderstorms may gradually return Thursday night or Friday as a warm front approaches from the southwest. Temperatures should remain near or slightly below seasonal averages through Friday before warmer weather begins returning during the weekend.

Summary:

Hot and humid weather will produce heat index values between 100 and 109 degrees today. The heat continues Tuesday, mainly along and south of Interstate 70. The greatest chance for thunderstorms will be overnight tonight into Tuesday morning across northeastern Missouri and west-central Illinois. A few storms could produce damaging winds, isolated hail, and locally heavy rainfall, although it remains possible that the strongest activity stays north of the area. Cooler, drier, and much more comfortable weather arrives Wednesday and continues through Thursday.

First. Accurate. Trusted. That is your First Warn Forecast. Practice heat safety today and remain weather aware overnight, particularly if you live north of Interstate 70.

First Warn Forecast: Saturday, July 18, 2026
Heat and Humidity Continue Through Early Next Week
Scattered Thunderstorms Possible Today and Sunday
Relief from the Heat Arrives by Midweek

The familiar midsummer weather pattern continues across the region with hot, humid afternoons and daily opportunities for scattered showers and thunderstorms. While widespread severe weather is not expected this weekend, a few stronger storms could produce gusty winds, frequent lightning, and brief heavy rainfall. The bigger story for many will be the persistent heat, with heat index values climbing between 100 and 105 degrees through at least Tuesday in many communities.

Today begins with plenty of sunshine before clouds build during the late morning and afternoon. As temperatures rise into the lower and middle 90s, isolated to scattered thunderstorms are expected to develop, especially along and south of Interstate 70. Not everyone will see rain, but any storm that develops will be capable of producing brief torrential downpours, dangerous lightning, and wind gusts strong enough to bring down small tree limbs. Storms will move slowly, which could lead to localized pockets of heavy rainfall, but the overall risk of flash flooding remains low.

A weak cold front will slowly slide into northeastern Missouri and west-central Illinois this evening, bringing another opportunity for scattered thunderstorms. However, because the front arrives after the hottest part of the day, storms should gradually weaken as the evening progresses.

Heat will once again be a major concern today. Afternoon temperatures will reach around 90 to the middle 90s, while the combination of heat and humidity will push "feels like" temperatures to around 100 to 105 degrees in many locations. If you have outdoor plans, drink plenty of water, take frequent breaks in the shade or air conditioning, and remember to check on neighbors, children, and pets during the hottest part of the afternoon.

Sunday brings little change to the overall pattern. The front is expected to stall near the Mississippi River, serving as a focus for another round of scattered showers and thunderstorms during the afternoon and evening. Forecast confidence in exactly where storms develop is lower, but any stronger storm could once again produce gusty winds and locally heavy rainfall. While widespread severe weather is not anticipated, lightning and isolated strong wind gusts remain the primary hazards.

One notable difference on Sunday will be temperatures. Areas west of the stalled front, primarily across Missouri, will continue experiencing dangerous heat with heat index values between 100 and 105 degrees. Meanwhile, communities farther east into portions of Illinois should enjoy slightly cooler temperatures, with highs remaining in the 80s and noticeably lower heat index values.

Looking ahead, Monday is shaping up to be the hottest day of the stretch. Widespread lower to middle 90s are expected, with heat index values climbing between 100 and 107 degrees. Heat Advisories may become necessary for portions of the region if confidence continues to increase.

Tuesday brings one final day of heat before another cold front sweeps through the region. That front will also bring a better chance for showers and thunderstorms, and unlike this weekend, there is a growing signal that a few stronger storms could develop if enough instability builds ahead of the front. We'll continue monitoring that potential over the next couple of days.

By Wednesday, a refreshing change arrives. Cooler temperatures, lower humidity, and highs back in the 80s will provide a welcome break from the recent stretch of oppressive summer heat. Dry weather is expected through much of Wednesday before small chances for showers gradually return later in the week.

What You Need to Know
Hot and humid conditions continue through Tuesday, with heat index values between 100 and 105 degrees.
Isolated to scattered thunderstorms are possible this afternoon and again on Sunday.
The strongest storms may produce gusty winds, dangerous lightning, and brief heavy downpours.
Monday is expected to be the hottest day of the forecast period, with heat index values reaching as high as 107 degrees.
A cold front arrives Tuesday, followed by cooler, less humid weather beginning Wednesday.

First. Accurate. Trusted. That's your First Warn Forecast. Continue practicing heat safety over the next several days, and keep an eye on the sky each afternoon as scattered thunderstorms develop. We'll continue refining the forecast as we get closer to Tuesday's cold front and the welcome relief arriving by the middle of next week.

First Warn Forecast: Tuesday, July 14, 2026

Summer is settling into a familiar pattern across the region with warm afternoons, increasing humidity, and only isolated opportunities for rain through the middle of the week. While temperatures will remain close to what we typically expect for mid-July, it will begin feeling noticeably more uncomfortable by Thursday and Friday as heat index values climb into the 100 to 105 degree range.

Today will feature a mix of sunshine and a few fair weather clouds with afternoon highs reaching the upper 80s to around 90 degrees. Humidity will slowly increase through the day, making it feel closer to 95 to 100 degrees in parts of southwest Illinois during the afternoon. Despite the added moisture, high pressure remains firmly in control, keeping the vast majority of the region dry with no significant weather concerns expected.

Wednesday looks very similar with another warm and humid day. Most communities will stay dry, although a few isolated afternoon showers or thunderstorms could develop across southern Missouri and the Ozarks. Any storm that manages to form will be brief but capable of producing a quick heavy downpour thanks to the abundant tropical moisture in the atmosphere. Most neighborhoods, however, will never see a drop of rain.

By Thursday and Friday, humidity continues to build while the protective ridge of high pressure weakens just enough to allow scattered afternoon and evening showers and thunderstorms to develop. Rain coverage will increase into the 30 to 60 percent range, but this is not expected to be an all-day rain event. Many locations will remain dry for much of both days, with storms developing mainly during the hottest part of the afternoon and early evening.

The primary concern with any storm will be torrential rainfall. The atmosphere will contain an exceptional amount of moisture, allowing storms to produce rainfall rates of one to two inches per hour. While widespread flooding is not anticipated, localized flooding could develop in areas that have recently received heavy rain or where storms repeatedly move over the same location. Frequent lightning will also accompany any thunderstorm, but the overall threat for widespread severe weather remains low at this time.

Looking ahead to the weekend, forecast confidence begins to decrease as subtle weather disturbances approach from the northeast. At this point, temperatures may ease back slightly by Sunday, and rain chances appear to become more isolated, but the exact timing and coverage remain uncertain.

What You Need to Know
Warm, seasonable afternoons continue through Wednesday with highs in the upper 80s to around 90.
Humidity steadily increases, with heat index values nearing 100 degrees today and Wednesday, then climbing into the 100 to 105 degree range Thursday and Friday.
Scattered afternoon and evening thunderstorms become more common Thursday and Friday.
Storms will be capable of producing brief torrential downpours, localized flooding, and dangerous lightning, although widespread severe weather is not expected.
Plenty of dry time is still expected each day despite the increasing rain chances.

First. Accurate. Trusted. That's your First Warn Forecast. Stay weather aware later this week, stay hydrated during the increasing heat, and continue checking back for updates as we fine-tune the timing and coverage of late-week thunderstorms.

Week geek out!

Two unique features in the Pacific Ocean happening at the same time.

The first is known as the blob which is a massive marine heatwave in the Pacific. This ocean anomaly alters the atmospheric pressure, pushing the jet stream north.

The second is the impressive El Niño which could be unprecedented.