textproduct: Sioux Falls

KEY MESSAGES

- Hot conditions continue into the weekend. Highs in the 90s to around 100 expected, with Friday the hottest day. Dew points remain a bit below seasonal normals, aiding in lower relative humidity. Continue to take precautions from the heat to reduce risk of heat illness.

- Very patchy morning valley fog is possible daily, but widespread dense fog remains unlikely. Fog could reduce visibility below two miles at times.

- Precipitation is very unlikely (less than 10%) through Saturday night. Shower and storm chances return Sunday evening and night, but confidence is low on the details.

UPDATE

Issued at 306 AM CDT Thu Jul 16 2026

Patchy fog with visibility below two miles has developed once again this morning, mainly focused in and near river valleys. Similar to the last few mornings, expect any fog to lift through 8-9 AM. Temperatures are in the mid 60s and 70s.

Minor adjustments again to the temperatures for today, lowering them a degree or two from the NBM as NBM has remained a bit too high the last couple of days. However, no significant impacts on heat indices, which remain in the 90s for the entire area. CAMs show some potential for showers today, but expect the result to be diurnally driven cumulus since soundings are very dry and there isn't much in the way of instability/forcing.

Friday still looks to be the warmest day, with the potential for heat headlines. Toward the weekend, fropa early Saturday brings northerly flow back to the area and slightly cooler but still above average temperatures. Also monitoring the potential for wildfire smoke to impact the area - confidence in significance and impacts is low at this time. Additional smoke may move in Sunday with increasing northwesterly flow aloft. Guidance remains quite varied in the details, but still looking like rain/storm chances return later in the day/night Sunday.

DISCUSSION

Issued at 150 PM CDT Wed Jul 15 2026

Very little change to the forecast for the next several days as upper level ridging continues to produce hot temperatures. So far with dew points mostly in the 60s, heat indices and heat risks have remained a bit muted, but if you need to be outdoors take any necessary heat precautions as it is still in the 90s. With a bit stronger southerly wind tonight and Thursday night overnight lows will trend warmer, likely only falling to 70 to 75 degrees. Fog chances may be lower as well because of the wind.

Friday will see a front approach from the north as northwest flow aloft increases a bit, which should aid in bringing surface winds around to a bit more southwesterly direction. This should help with deeper mixing and likely higher temperatures, with most locations climbing to 95 to 102 degrees, warmest in central SD. Right now Friday appears to see the best chance for a heat headline. This front will slide into the area Friday night into Saturday morning, but is not expected to produce any showers or storms.

A bit better dip in upper level flow moves through Sunday night which looks like the best chance for isolated to scattered showers and storms. For now Sunday appears to be on the dry side with any shower and storm chances moving in Sunday night. There some hints of elevated moisture and very weak instability on Sunday morning around 10-15 kft which could produce some weak ACCAS showers, but confidence very low on this.

Stronger west and northwest flow aloft continues along the Canadian border into northern MN early next week, possibly becoming a bit more pronounced by Monday night into Wednesday. This should support temperatures back to around normal or maybe a touch below. This may bring some patchy showers and storms to the area as well.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 605 AM CDT Thu Jul 16 2026

Patchy valley fog through 13-14z will lead to some brief MVFR and lower visibility. Otherwise, VFR conditions expected with diurnal cumulus this afternoon into the early evening. Additional valley fog possible again Friday morning.

Southerly winds gust 15-20 knots this afternoon.

FSD WATCHES/WARNINGS/ADVISORIES

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