Active Weather
Three things are happening in this region at once today: heat through the afternoon, storms in the evening, and a flooding risk over Iowa that connects the two.
The National Weather Service active alert feed, read at 1:01 this morning Eastern time, counts seven active alerts in Kansas, five in Missouri, two in Iowa, and two in Nebraska.
Start with the heat. An extreme heat warning covers parts of central, east central, north central, and northeast Kansas until 7:00 tonight Central time with heat index values up to 109. A second extreme heat warning covers east central and northeast Kansas and west central Missouri, including the Kansas City area, until 8:00 tonight with heat index values up to 106. Heat advisories cover nine counties in central and south central Kansas with values to 105, and southwest Iowa with southeast Nebraska from 1:00 to 7:00 this afternoon with values to 108.
An extreme heat warning is the higher of the two products. It means heat illness becomes significantly more likely, including for people who are not working hard outdoors. Heat index is what the air feels like once humidity is counted, and in this region the humidity is what pushes an ordinary September afternoon into warning territory.
Now the storms. The Storm Prediction Center's outlook for today, issued at 12:46 yesterday afternoon Central time, places a marginal risk of severe thunderstorms from the central Plains into the Upper Midwest, with Omaha, Lincoln, and Des Moines inside it. The center expects severe potential to increase during the evening ahead of a cold front across Iowa, eastern Nebraska, and possibly northern Kansas. Early storms should carry isolated large hail and strong gusts, then grow into lines with a greater damaging wind threat later in the evening.
Marginal is the lowest of five severe categories. It means isolated severe storms rather than a widespread event. The specific thing to expect from a line of storms in the evening is wind, and wind is what takes the power out.
One severe thunderstorm warning was active in Iowa at the time the feed was read, from the overnight round of storms moving in from South Dakota.
The Weather Prediction Center's excessive rainfall discussion, issued at 8:57 last evening Eastern time, holds a slight risk of excessive rainfall over Iowa today into tomorrow morning. Slight is the second of four levels and it is a step above the marginal risks elsewhere in the country. It reflects moisture running well above normal, with the storm breeding ground east of the Nebraska Sand Hills the focus and flash flood guidance in the two to two and a half inch range over six hours.
Infrastructure
No large wildfires are burning in the four states on the National Interagency Fire Center's current incident list.
The national wildfire preparedness level is 4 on a five step scale, set September 4 at 7:30 in the morning Mountain time, according to the National Interagency Fire Center. Its national fire news page, current September 7, counts 65 large fires with 15,855 firefighters and support staff assigned, and 53,233 fires for 8,303,398 acres so far this year.
Federal disaster declarations are open in all four states from summer storm events. Kansas carries numbers 4940 and 4943, Missouri number 4939, Iowa number 4942, all issued September 1, each for severe storms, straight line winds, and flooding, with tornadoes named in the Kansas declarations. Households in the named counties can look up the assistance categories and application deadlines under those numbers.
The infrastructure item for this evening is straightforward. A line of storms carrying damaging wind gusts across Iowa and eastern Nebraska in the evening is the kind of event that drops distribution lines and leaves scattered outages overnight. Charging phones and battery banks this afternoon, while the power is on and before the storms arrive, is the whole preparation.
If the power does go out during heat, the freezer holds about 48 hours if it is full and the door stays closed, and about 24 hours if it is half full. The refrigerator holds about four hours. Opening the door to check resets the clock.
Public Health
Two air quality alerts are active in Missouri. The St. Louis Clean Air Partnership has issued an orange level ozone alert for the St. Louis metropolitan area from 10:00 this morning to 8:00 tonight Central time, covering St. Charles, Franklin, St. Louis, St. Louis City, and Jefferson counties on the Missouri side.
Orange means ozone is forecast to reach levels that pose a health risk. Ozone peaks in the afternoon on hot sunny days. People with asthma, older adults, and children feel it first. Moving outdoor exercise to the morning removes most of the exposure, and evening is fine because ozone breaks down after dark.
The heat and the ozone stack on each other today, and they affect the same people. Anyone with a lung or heart condition in the Kansas City or St. Louis areas has a good reason to stay indoors this afternoon.
For heat generally: drink before you are thirsty, take shade breaks on a schedule rather than by feel, and check on anyone older or living alone. When sweating stops during heat exposure, that is a medical emergency rather than a sign of cooling off.
No boil water advisories were identified across the region.
The Centers for Disease Control and Prevention Health Alert Network archive could not be read this run, so this brief makes no claim about national health advisories in either direction.
Watch Item
The near term item is tonight, and the medium term item is the heat.
Tonight, a line of storms with damaging wind is the expected outcome across Iowa and eastern Nebraska, with flash flooding possible where the heaviest cells train over the same ground. That combination is why Iowa carries the only slight risk of excessive rainfall in the country today. The practical version: know where you would shelter if a severe thunderstorm warning is issued for your county, which is an interior room on the lowest floor away from windows, and do not drive into water across a road. That last one is the National Weather Service's Turn Around, Don't Drown guidance and it is the one that keeps costing lives in this region every year.
Further out, the Weather Prediction Center's extended discussion, issued at 1:41 yesterday afternoon Eastern time, keeps the long duration heat wave over the Mid and Lower Mississippi Valley and the southern Plains through much of the week, with widespread major to extreme HeatRisk and several record minimum and maximum temperatures in the forecast. There is some trend toward relief in northern areas by the weekend, which for this region means Nebraska and Iowa may cool before Kansas and Missouri do.
Record warm nights are the part that matters. A heat episode gets more dangerous on its third and fourth day because the house never cools down overnight and the body never recovers. If your air conditioning is struggling, today is the day to deal with it rather than Thursday.
The center also flags a stronger pattern change for early next week: a cold front pushing south across the northern Plains late this week, then low pressure strengthening over the northern and central Plains, with heavy rainfall potential over the eastern Plains and the Upper Midwest early next week. That is far enough out to be a watch item rather than a plan.
Explore Today
Why day three of a heat episode is worse than day one, and what to do about it.
Where to shelter, and why damaging wind matters more than hail for most households.
Flash flooding on a slight risk day, and the road crossing that catches people out.