Moisture pooled in the vicinity of a nearly stationary boundary early on July 21, which slowly worked northward as a warm front over the next two days while a large upper level ridge expanded across the Northern Plains. Most areas experienced heat index values from 100 to 115 degrees, with the most consistent and highest heat index values on the afternoon of July 23 across far southeast South…
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS FSD wrote it up.
Moisture pooled in the vicinity of a nearly stationary boundary early on July 21, which slowly worked northward as a warm front over the next two days while a large upper level ridge expanded across the Northern Plains. Most areas experienced heat index values from 100 to 115 degrees, with the most consistent and highest heat index values on the afternoon of July 23 across far southeast South Dakota, northwest Iowa, and northeast Nebraska.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Sioux Falls, SD wrote its last area forecast discussion before the first event at Jul 20, 12:45 PM CST, 22 hours 15 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Sioux Falls SD 145 PM CDT Sun Jul 20 2025 .KEY MESSAGES... - Cluster of elevated thunderstorms may try to become surface based this afternoon, owing to potential for increased hail potential and some wind potential into areas of eastern South Dakota this afternoon. Still very uncertain on future progression. - Scattered thunderstorms remain possible into the evening and overnight hours, though great uncertainty remains on development and track. Level 2 (slight) risks more likely west of the James River, with Level 1 (marginal) risks most areas due to uncertainty. - Greatest hazards will be 1-2" hail initially with a transition to clusters of storms with 60 to 70 mph winds overnight. - An active pattern remains in place for much of the upcoming week, with nearly daily thunderstorm risks, but lower probability of pin pointing exact locations and times of impact. - Temperatures and humidity also rise this week with the warmest temperatures and heat risk levels Monday afternoon, but especially Tuesday. Advisories and warnings will be possible. && .DISCUSSION... Issued at 141 PM CDT Sun Jul 20 2025 THIS AFTERNOON: Ongoing elevated cluster of convection along and north of Highway 14 continues early this afternoon. This convection on the edge of an area of steep mid-lvl lapse rates, appears to be driven east by a weak shortwave, but also persistent west southwest 700 mb flow. Considerable uncertainty remains on the eastward and southward progression of this convection, as inhibition south of Highway 14 to Interstate 90 is expected to weaken slightly through the afternoon but still remain in place. However, most of this convection is also following the track of the northern edge of enhanced 850mb moisture which will continue to pivot north and east and bring it along and just south of Highway 14 this afternoon. Severe potential remains more uncertain, however western and southern edges of this cluster would favor some intensification with a more direct influence of deeper instability pool to the southwest and more potential to become surface based. 1.5" hail could be a likely risk in any stronger storm, but could envision some potential for linear formation given increasing 700:500 flow. The evolution of this area of convection is still very much in doubt. EARLY EVENING/TONIGHT: The aforementioned convective cluster adds further uncertainty into the evening and overnight hours, as it will likely leave an elongated differential heating boundary stretching westward along or north of I-90 into the West River areas. As diurnal temps are reached late this afternoon, and convergence ahead of a forming low and dryline in the panhandle, isolated to scattered convection may form over northern Nebraska and southern South Dakota and drift eastward or northeastward. This strong to severe convection will reside in a moderate area of instability but somewhat marginal shear. Initial 1-2" hail risks likely transition towards a wind risk. Additional convection could also form on the aforementioned boundary near or north of I-90, which would have some preference to tracking southeast. Other convective clusters may form off the western High Plains overnight and move eastward, however given the increasing EML the eastward progression of convection into the Tri-State area remains highly uncertain. All-in-all, there is poor resolution of the next 24 hours in most, if not all, CAM guidance. MONDAY: The broad mid-lvl ridge continues to build early Monday, with some guidance suggesting northern and northeastern areas of the CWA still within a risk for impacts from a trailing MCS that crosses the Dakotas overnight and into mid-morning Monday. However, another scenario is that capping wins out and any MCS stays well north of the CWA. Either way, we'll be dealing with considerable low lvl stratus through the morning and a lingering elevated shower/thunderstorm risk on the LLJ axis through mid morning. Heights will rise in the afternoon as temperatures begin a steady upwards climb towards the 90 degree mark. The reach of the warmest air will depend a bit on how quickly stratus erodes, but with rising dew points, heat index values could approach advisory criteria south of I-90 in the afternoon/early evening. Isolated convection may reform on a developing stationary boundary over central and northern South Dakota early in the evening and track north and east. TUESDAY: The greatest convection risks likely take place north of Highway 14 Monday night into Tuesday morning as another MCS crosses the Northern Plains, but isolated showers/thunderstorms on the LLJ axis will again be possible at daybreak. Further south, a frontal boundary will spreads northeast out of western Nebraska into northeastern SD by the afternoon. South of this boundary, very warm and very humid airmass will build, with a high probability of heat advisory to extreme heat warning criteria met Tuesday afternoon. Depending on the extent of capping late Tuesday into Wednesday, convection will also be possible, but may be more focused along and west of the stationary front into central and northern South Dakota Wednesday morning. Any convection that forms will be at the mercy of subtle low-predictabilty vorticity maxima moving through the southwesterly flow. WEDNESDAY-SATURDAY: A continued messy forecast remains in the cards for the rest of the week and into next weekend, as mid-lvl heights build, but remain flattened enough to allow several waves to exit the West Coast trough. Confidence continues to remain lower than normal through the week, but some focus on PoPs is centered around Wednesday night into Thursday and again Friday into Saturday. Temperatures are favored to remain above normal through the period, and with dew points remaining at peak mid- late July levels, every day may feel hot and humid. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1131 AM CDT Sun Jul 20 2025 MVFR to IFR ceilings continue to focus in areas along and south of I-90 at mid-day. Meanwhile, a potent shortwave crossing the ND/SD border will continue to push convection eastward into the afternoon. Given the progression of low-lvl northeast, it's not impossible that this convection may try to build southeast into the Highway 14 corridor later this afternoon. Additional convection may develop over central SD on the trailing outflow from this boundary later this afternoon and evening, but overall forecast confidence remains low. Overnight, we'll see a return of MVFR to IFR ceilings moving north which are likely to stay in place deep into Monday morning. Convection risks overnight are so uncertain in both development and coverage to preclude any mention overnight above a prob30. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && DISCUSSION...Dux AVIATION...Dux
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Service Notice</title>
<link rel="stylesheet" href="index.css">
</head>
<body>
<main class="wrap">
<section class="card" role="status" aria-live="polite">
<div class="status" id="status">Temporary Notice</div>
<h1 id="headline">This service is currently unavailable.</h1>
<p id="message1">
The site you requested is temporarily down for maintenance or an unexpected outage.
</p>
<p id="message2">
Please try again in a few minutes.
</p>
<p class="small" id="detail">
If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
</p>
</section>
</main>
<script src="index.js"></script>
</body>
</html>The national radar mosaic for the moment the first event began.
1 excessive heat, 1 heat. Local standard time, as filed.
Dangerous heat index readings reached afternoon peaks as high as 105 degrees near Dakota City on July 23.
Heat index values peaked during the afternoon hours of July 23 as high as 101 degrees near Concord.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Nebraska in 2025Every state in 2025This day in weather historyWarnings in Nebraska, July 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 1288558, 1288559.