textproduct: Sioux Falls

KEY MESSAGES

- Near to slightly below normal temperatures prevail through Saturday. A couple spotty shower and storm chances will also be possible during this time.

- An extended period of heat and humidity is expected starting Sunday into next week. Heat indices up to the low 100s could lead to moderate to major heat risk at times.

- An active pattern aloft will lead to isolated chances for stronger storms by early to midweek. However, some uncertainty remains.

UPDATE

Issued at 955 PM CDT Thu Jun 25 2026

Still have some very spotty sprinkles along the Missouri River Valley west of Vermillion, with additional spotty light showers in central SD drifting northeast. With relatively high cloud bases, chances for measurable rain overnight into Friday seem slim, but could see scattered sprinkles over mainly southeast SD through midday Friday.

Cloud cover will diminish in the afternoon, allowing for better warming than many areas saw today, with highs Friday in the upper 70s-lower 80s most areas. Slightly warmer Saturday, though highs are somewhat uncertain as there are hints that we could see stratus become more expansive in a moist southeast-southerly low level flow.

A much more significant warm-up is still on tap early next week, though just how warm is the question. LREF mean ensemble temps are a few degrees shy of the latest NBM data, though this would still put highs well into the 90s Sunday/Monday. While these look to be the warmest days of the upcoming week, we are likely looking at a prolonged stretch of days with highs in the 90s as we head into the first days of July. Moderate to high humidity levels and persistent southerly breezes will limit temperature drops at night, with daily lows in the upper 60s/70s providing little relief. As a result, Heat Risk levels look to push into the Moderate to Major category (level 2/3 of 4) on Sunday, and remain there with pockets of Extreme (Level 4 of 4) Heat Risk possible from Monday onward. Those with outdoor activities or work planned, or vulnerable individuals with higher sensitivity to heat, should be preparing for multiple days of potential heat impacts.

DISCUSSION

Issued at 215 PM CDT Thu Jun 25 2026

CURRENTS & TONIGHT: Beautiful conditions continue! Taking a look across the area, fall-like conditions continue this afternoon with many sites reporting temperatures in the low to upper 70s with lighter winds as of 1 pm. We're also starting to see some scattered showers progress into the Missouri River Valley mainly in response to weak shortwave and weakening LLJ. While severe weather is not expected, could see this festering activity continue through the early evening mainly across the same areas before things gradually dissipate with the loss of diurnal heating. Otherwise, could see additional showers develop overnight into Friday morning as another wave interacts with a strengthening nocturnal LLJ. Lastly, more seasonable temperatures are expected overnight as lows fall into the mid to upper 50s for the night.

THE WEEKEND: Looking into the weekend, we'll continue to see a few lingering showers in our far northwestern zones to start the day on Friday. As the LLJ weakens, this activity should gradually diminish by mid-morning. Quieter conditions will return for the rest of Friday into the first half of Saturday as highs continue to sit in the low to mid 80s. Otherwise, cloud cover will gradually build during the day on Saturday as warm air advection (WAA) strengthens. With southwesterly flow in place aloft, increases in isentropic lift with an approaching wave could lead to a few pockets of drizzle to light shower developing in the lower cloud deck. However, severe weather is not expected mainly due to strong cap according to soundings. Looking into Sunday, the focus will shift to the building heat as southerly surface winds and increasing mid-level WAA leads to a push towards highs mainly in the low to upper 90s. This combined with dew points closer to upper 60s to low 70s will lead to heat indices in the 90s to low 100s for parts of the area with the warmest conditions across northwestern IA. While a heat headline could be needed, decided to forgo it at this time mainly due to uncertainty with spacial extent. Nonetheless, with muggy conditions expected through Sunday evening make sure to stay hydrated and to limit any strenuous activities!

NEXT WEEK: Heading into the extended period, the focus will continue to be on the heat as upper-level ridging continues to build over the eastern CONUS. With southerly surface winds in place and multiple pushes of warmer air aloft, expect temperatures to continue to hover in the low to upper 90s from Monday onwards with heat indices (Hi) in the 90s to low 100s degree marks at times. While conditions won't quite make it into excessive heat territory, we could see many areas touch heat advisory criteria (HI>100) at times each day so this will be something to watch moving forward. Either way, the conditions will lead to moderate to major heat risk for most areas from Monday through Wednesday so make sure to drink plenty of water and to take plenty of breaks when working outdoors! Otherwise, we'll also have to keep any eye to the skies through midweek as south-southwesterly flow aloft help ushers in multiple pieces of energy into the area through weak perturbation. With plenty of heat in the forecast, all that's needed is a strong enough trigger to break through the cap to get something strong to severe. Nonetheless, its still uncertain if this can happen given the warmer temperatures +20 to +28 degrees C at 800 mb through midweek. With all this in mind, make sure to monitor your local forecast as things will be subject to change moving forward.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1230 AM CDT Fri Jun 26 2026

VFR conditions are expected through the period with scattered light showers or sprinkles mainly along/west of I-29 at times through midday Friday. Light and variable winds will settle around to southeast by mid-late morning with occasional gusts around 20kt west of I-29 Friday afternoon through sunset.

FSD WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None. IA...None. NE...None.