textproduct: Sioux Falls

KEY MESSAGES

- Summer heat and humidity will make its return starting Sunday into next week. Heat indices up to the low 100s will lead to Major to Extreme Heat Risk. Begin planning now to reduce the risk of heat illness and impacts.

- An isolated chance for stronger storms will be possible from Saturday night into Sunday. Primary risks would be up to golf ball sized hail and damaging winds up to 65 mph.

- An active pattern aloft could lead to additional chances for stronger storms from early to mid next week. However, some uncertainty still remains.

DISCUSSION

Issued at 222 PM CDT Fri Jun 26 2026

CURRENTS & TONIGHT: A warm and breezy day continues! Taking a look across the area, we're continuing to see a few sprinkles to very light showers lift out of portions of far eastern SD and southwestern MN this afternoon with mainly light accumulations. While this very light activity could persist for the next hour or two, should see most of this activity push out of our area by late afternoon. From here, mostly quiet conditions will return as cloud cover thins into the evening hours. Otherwise, weak mid-level ridge will shift our quasi-zonal flow aloft back to more southwesterly overnight setting the stage for our next precipitation chances from Saturday into Sunday. Lastly, a warmer night will be on tap as overnight lows only fall into the upper 50s to mid 60s.

SATURDAY & SUNDAY: Looking into the rest of the weekend, quieter conditions will temporarily return by Saturday as weak ridging move overhead. Cloud cover will gradually increase during the day as a lifting warm front bringing in strengthening warm air advection (WAA). This combined with deeper mixing and a tightening SPG will not only lead to the return of breezy southeasterly winds, but also a slight bump in temperatures with highs peaking in upper 70s to mid 80s. Looking aloft, southwesterly flow will lead to multiple pieces of energy lifting out of the Black Hills into northeastern SD. While we can't completely rule out some isolated showers in our far northwest during the afternoon, the main concerns will develop from Saturday evening into Sunday morning as a developing triple point lifts out of the Nebraska Panhandle with a surface low. Given the slightly weaker cap and strengthening LLJ, current thoughts are that the increasing forcing with the triple point could be enough to break the cap and generate a few thunderstorms by Sunday morning.

IF storms can develop, they could become strong with a decently unstable environment characterized by around 1200-1800 J/kg of CAPE and around 40-50 kts of 0-6 km bulk shear. Stronger storms would be capable of producing up to golf-ball sized hail and damaging wind gusts up to 65 mph. Nonetheless, there are still some locational differences between short-range guidance so its a bit hard to pin down a specific area of focus right now. With all this in mind, most of our area is now outlined in an SPC Day 2 Marginal Risk (Level 1 of 5) for severe weather so make sure to multiple ways to receive warning information! From here, quieter conditions should return from late morning onwards as the upper-level ridge strengthens setting the stage for a return of dangerous heat. While the early morning storms could potentially affect our temperatures, southerly surface winds combined with a push of strong WWA aloft could boost our highs to the low to upper 90s with heat indices in the 90s to low 100s. While this would fall into our heat advisory criteria, will likely wait until things get closer to finalize any type of heat headline. Lastly, given the warmer overnight temperatures (60s- 70s); we'll have to be on the lookout for a few record warm lows across the area from Sunday into Monday (check climate section below.)

NEXT WEEK: Heading into the new week, 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 Thursday so make sure to drink plenty of water and to limit any strenuous activities! Otherwise, we'll also have to keep any eye to the skies through late week as south-southwesterly flow aloft helps ushers in multiple pieces of energy into the area through weak perturbations. With plenty of heat in the forecast, all that would be needed is a strong enough trigger to break through the cap to get something strong to severe. While the probabilities of this are low (30% or less) at this time, the chances aren't zero either so make sure to monitor you local forecast for the latest changes.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1230 PM CDT Fri Jun 26 2026

Mainly VFR conditions will transition to mainly MVFR and lower by Saturday. Looking at satellite imagery, pockets of drizzle to very light showers continue to progress eastwards this afternoon giving way to making VFR cigs in its wake. Additional MVFR cigs and lower will return overnight with the potential for a few additional spits. However, the probabilities are too low (<30%) to include in the TAFs. Lastly, southeasterly winds will become periodically breezy at times with gusts between 25-35 mph expected through Saturday.

CLIMATE

Issued at 222 PM CDT Fri Jun 26 2026

Building heat across the area from Sunday onwards will lead to the increased potential for a few temperature records being either tied or set:

Record Highs:

Monday (06/29): KFSD(101|2002) KSUX(100|2022)

Wednesday (07/01): KFSD(97|1948) KSUX(101|1911) KMHE(100|1900)

Thursday (07/02): KFSD(101|1911) KSUX(99|1911) KHON(100|2012)

Record Warm Lows:

Monday (06/29): KFSD(77|2020) KSUX(80|1931) KHON(75|2020)

FSD WATCHES/WARNINGS/ADVISORIES

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