textproduct: Sioux Falls

KEY MESSAGES

- An extended stretch of hot temperatures continues through late this week. Highs in the 90s to 100 degrees expected. The cumulative nature of the heat could lead to some heat health concerns.

- Patchy morning fog is possible each day, but widespread dense fog remains unlikely.

- Minimal precipitation is expected over the next 7 days, with the LREF probability of >0.25" through Monday the 20th no greater than 20% in any one location.

UPDATE

Issued at 244 AM CDT Sun Jul 12 2026

No significant changes to the forecast early this morning. Winds have remained a bit elevated thus far, so have not seen much in the way of fog. However, much of the hi res guidance this morning continues to show at least spotty fog development in the river valleys and into northwestern IA. Widespread dense fog is not expected but some locations could see visibility once again this morning below two miles. Temperatures are in the upper 60s and 70s with clear skies.

Minor adjustment (a degree or two) to the forecast lows this morning through the next couple of mornings, with the warmer soil temperatures and forecast/ob trends. Confidence remains high in the continued warm and dry conditions through much of next week, with highs in the 90s to lower 100s and lows in the upper 60s and 70s. Relatively lower humidity still keeps heat indices just below criteria through the early part of the week, but will continue to monitor trends as warmer days are expected by mid week. Additionally, numerous days of dry and hot conditions may lead to some locally elevated fire concerns as finer fuels begin to dry.

With lots of sunshine, those spending time outdoors should take precautions to limit both sun and heat exposure with high UV index in addition to the hot temperatures.

DISCUSSION

Issued at 1221 PM CDT Sat Jul 11 2026

THIS AFTERNOON: It's a hot day across the region with plenty of sunshine. High temperatures climbing into the 90s in most locations, but with dew points mixing down lower into the 60s, heat index values remain below critical values. That said, anyone spending time outdoors over the next days will need to take preventative actions from a very high UV index.

TONIGHT: Winds again turn light and variable through the night. The NBM has been biased a bit too cold with overnight lows the past days, but we will begin to see dew points lower a bit at night which could lead to some lows into the upper 60s. HREF probabilities show less potential for fog this morning than last night, however, the favored areas would again be across NW Iowa for patchy morning fog.

SUNDAY: Pretty much an identical day on Sunday, with a bit more southwesterly wind fetch west of I-29. This will result in high temperature creeping a couple degrees warmest west of I-29. However with deeper mixing, dew point mix downwards further, and will again keep heat index values below critical thresholds.

MONDAY-FRIDAY: Really no major changes in the forecast for the upcoming work week. The mid-lvl ridge continues to build through the Northern Plains centering itself along the ND/SD border by Monday and then building southward and broadening by the middle of the week along I-90. The result will be daily highs in the 90s to even lower 100s in a few areas west of I-29. The daily direction of the surface winds will dictate some variance in warming, with southwesterly wind fetch allowing for deeper mixing and slightly higher afternoon highs. Records this week appear to be safe even if 100s are reached. Most records for the upcoming week range from 104-113 degrees stemming from some severe past drought years). Fortunately no extreme rises in dew points are expected, which will keep heat index values below 100 degrees in most areas. Will consider heat headlines for portions of the James River valley areas and westward by Monday where highs do begin to cross the 100 mark, but heat index values remain 1-3 degrees below criteria. ECE/GEFS probabilities continue to highlight the James River valley with a 60%+ probability of exceeding 100 through Tuesday, however as southwesterly winds expand eastward late in the week, those probabilities to expand into the I-29 corridor. A side note with all of the heat concerns this week. Daily RH values do fall near or below 20% west of the James River into the week with afternoon wind gusts approaching 25 mph. We may begin to see some increase in fire danger given the dry out of fine fuels.

SATURDAY-SUNDAY: We may begin to see some break in the ridge by next weekend, as a weak mid-lvl wave flows northward through the Plains and a second wave crosses near the Canadian border. While this could bring some clouds to next weekend, low-lvl moisture transport through the Central Plains veers off quickly east, and the Canadian wave is only bringing limited Pacific moisture with it. Precipitation chances remain low at this point, with LREF guidance indicating no more than a 17% probability of >0.25" of precipitation through Monday morning.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 616 AM CDT Sun Jul 12 2026

Patchy and locally dense fog has developed in some of the valleys this morning as well as east of I-29. Very isolated visibility below one mile has been observed. Conditions should improve through 13-14z. Outside of this morning's fog, VFR conditions prevail with clear skies.

Southerly winds increase, with gusts 20 to 25 knots west of I-29.

FSD WATCHES/WARNINGS/ADVISORIES

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