textproduct: Sioux Falls

KEY MESSAGES

- Extreme Heat Warning through 9 PM this evening. Heat index values as high as 115 degrees. Heat Advisory parts of northeast NE, northwest IA, southwest MN and far southeast SD Monday afternoon/evening.

- While details are uncertain and confidence remains low, if storms develop in the late this afternoon and evening, some may be strong to severe with damaging winds, isolated large hail and locally heavy rain possible.

- Next threat for showers and thunderstorms will be on Thursday. An isolated storm could be severe.

DISCUSSION

Issued at 118 PM CDT Sun Jul 26 2026

The thunderstorm threat is still very low confidence for late this afternoon into tonight. Quite a bit of cloud cover has lingered into the early afternoon which is slowing heating. And, as opposed to yesterday, the mid to upper level wave today is a bit weaker and may not help to organize activity as efficiently, so will need to find a way to break the cap. For now these chances look best south of I-90 into northwest IA where the deeper moisture resides. South central SD shows the weakest cap late afternoon while parts of northeast NE, far southeast SD and northwest IA see a moderately increasing LLJ during the evening hours, which could focus some thunderstorm development.

Winds turn more northerly tonight into Monday which should allow dew points to settle into the 60s and lower 70s. This will likely keep heat indices in the 90s and thus heat headlines will not be necessary. One exception may be across parts of northeast NE and northwest IA where heat indices should creep above 100 again with the higher dew points. Will have a heat advisory for these locations.

Monday and Monday night should be quiet as more stable air settles in. One exception may be later Monday night in central SD as some upper level support spreads from western SD into that area. Just some small chances west of the James for now.

Tuesday and Wednesday will be on the northern edge of the upper level ridging which will keep some westerly flow aloft in place. This should allow for a couple of weaker waves to move through. While precipitation is unlikely, some occasional cloud cover and slightly suppressed temperatures will likely keep the more extreme heat and humidity at bay, so heat headlines for both of these days looks unlikely.

A stronger wave moves into the area Thursday and should be the next better chance for showers and thunderstorms. Should see some isolated severe storms with this activity.

Temperatures settle back to near normal Friday into next weekend as northwest flow aloft should bring much more comfortable air into the region with little chance for showers and thunderstorms.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 652 PM CDT Sun Jul 26 2026

Low confidence forecast continues for thunderstorm development through this evening. Chances for impacts continue to remain low, generally between a 20-30% chance, highest along the Missouri River Valley including KYKN to KSUX through about midnight to 2 am. Otherwise, patchy light fog may develop in a few spots heading towards daybreak, but chances for this are very low, generally less than 10% at this time.

Wildfire smoke currently over eastern Montana and western North Dakota has brought MVFR visibilities to those area. This smoke will likely dive southward heading into the day Monday; however, guidance currently shows it thinning out enough that even if some smoke makes it to the surface, visibilities will likely stay above 6SM. Trends will be monitored.

Winds will gradually turn light and variable through tonight, turning more northeasterly heading into the day on Monday. Winds will remain fairly light across the area through the daytime hours Monday, but could locally gust up to 20 kts in portion of south- central South Dakota Monday afternoon.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Extreme Heat Warning until 9 PM CDT this evening for SDZ038>040-050-052>071. Heat Advisory from 1 PM to 8 PM CDT Monday for SDZ070-071. MN...Extreme Heat Warning until 9 PM CDT this evening for MNZ071- 072-080-081-089-090-097-098. Heat Advisory from 1 PM to 8 PM CDT Monday for MNZ081-090. IA...Extreme Heat Warning until 9 PM CDT this evening for IAZ001>003-012>014-020>022-031-032. Heat Advisory from 1 PM to 8 PM CDT Monday for IAZ002-003- 012>014-020>022-031-032. NE...Extreme Heat Warning until 9 PM CDT this evening for NEZ013- 014. Heat Advisory from 1 PM to 8 PM CDT Monday for NEZ013-014.