textproduct: Sioux Falls

KEY MESSAGES

- A Heat Advisory is in effect for some areas today into Monday, and further adjustments to headlines are possible in the coming days.

- Isolated to scattered severe thunderstorms will be possible on Monday late afternoon into the evening. The better chances will be near and east of I-29.

- Summer heat and humidity is expected periodically through next week. Daily heat indices of 95 to 105 degrees will lead to Major to locally Extreme Heat Risk at times. Begin planning now to reduce the risk of heat illness and impacts.

- An active pattern through the week leads to periodic moderate chances for showers and storms. Uncertainty in the timing of rain also brings lower confidence in daily excessive heat.

DISCUSSION

Issued at 144 PM CDT Sun Jun 28 2026

Thunderstorm Risks:

Very warm and humid conditions in place today in the wake of the overnight MCS that brought a fairly widespread half an inch to 2 inches, with pockets around 3 inches. Even with the warm and humid conditions, drier air aloft and a general lack of upper level support suggest showers and thunderstorms will remain at bay. A very weak wave moves through parts of western IA tonight but moisture appears to be fairly scant with this. The more impressive wave is to the west of the area with storms looking to remain well west of the area as well.

This stronger wave pushes into central SD on Monday and brings another hot and humid day to the area. A trough of low pressure moves into the area at the surface as low pressure lifts northeast and could spark a few showers and thunderstorms. The better chances will be near and east of I-29 but once again will be fighting a bit of a cap. If storms do develop there will likely be close to 300 J/kg CAPE as well as moderate shear to support wind gusts to 70 mph and hail to the size of golf balls. Heavy rain will be a threat as well with the freezing level around 14000 feet AGL.

Tuesday night into Wednesday night may be the next period where more widespread chances for showers and thunderstorms returns. Models are fairly agreeable lifting a wave northeast into the area and only slowly exiting. This brings a somewhat extended period of warm advection in the lower levels. Instability appears to be sufficient around 2500 J/kg with weak to moderate shear. With the freezing level around 13000 feet AGL, heavy rain will also be a threat.

Another fairly well agreed upon wave ejects northeast on Thursday and may continue chances for thunderstorms. Friday into next weekend less agreed upon but continued pieces of upper level energy should move through the area bringing a continued threat for showers and thunderstorms.

Heat Risks:

Long story short, daily excessive heat is no guarantee this week given the southwest flow aloft and numerous weak waves which will likely spark showers and storms as well as produce additional cloud cover.

Monday will prove to be windy and hot with fairly high humidity. This should bring widespread heat indices of 95 to 105 to areas near and east of I-29. Heat indices west of I-29 will likely remain in the lower to mid 90s.

Tuesday will see a little drying in the low level as this Monday night wave lifts north and induces a little mixing in the low levels. While highs will again be in the 90s, lower dew points should bring a break from the higher humidity levels and likely keep heat indices in the 90s.

Wednesday will bring more question marks in regards to higher heat indices, more so the temperatures than the dew points. With the expected wave lingering around during the day, cloud cover, and possible precipitation, will bring about a lower confidence in temperatures climbing high enough to push us into more dangerous heat risk levels.

Thursday continues with a few question marks regarding excessive heat due to another wave as will Friday. Still likely daytime temperatures will climb into the upper 80s to mid 90s with some humidity, but the ability to produce widespread 100 + degree heat indices every day will be limited.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1202 PM CDT Sun Jun 28 2026

MVFR ceilings will gradually rise and lift northward through the afternoon. While tonight into Monday morning should see VFR conditions, the previous nights rainfall and generally lighter winds may allow for some IFR and MVFR ceilings and patchy fog. Confidence too low to include for now, bit something to keep an eye out for. Otherwise southerly flow will increase in most areas quickly Monday morning with gusts around 30 mph likely.

CLIMATE

Issued at 410 AM CDT Sat Jun 27 2026

Summer heat builds into the area from Sunday through much of next week. This will lead to a potential for a few temperature records to be tied, or possibly broken:

Current Record Highs:

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

Current Record Warm Lows:

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

FSD WATCHES/WARNINGS/ADVISORIES

SD...Heat Advisory until 9 PM CDT Monday for SDZ062-066-067-069>071. Heat Advisory until 9 PM CDT this evening for SDZ060-061-065- 068. MN...Heat Advisory from 1 PM to 9 PM CDT Monday for MNZ072-080-081- 089-090-098. IA...Heat Advisory until 9 PM CDT Monday for IAZ001>003-012>014- 020>022-031-032. NE...Heat Advisory until 9 PM CDT Monday for NEZ013-014.