textproduct: Duluth

KEY MESSAGES

- Widespread frost this morning away from Lake Superior with some locations falling to freezing or just below. Another round of frost expected Wednesday morning, but not as widespread.

- Persistent northeasterly winds will keep the threat for rip currents in place at Twin Port beaches today and may linger into Wednesday as well.

- Precipitation chances return late Wednesday into Thursday with the potential for scattered light showers.

DISCUSSION

Issued at 241 AM CDT Tue Sep 22 2026

Early this morning, widespread frost is occurring across much of the Northland away from Lake Superior, as clear skies and light winds have allowed temperatures to drop into the low 30s and even a few upper 20s as of 2 AM. A Frost Advisory remains in effect until 8 AM. Stratus has formed in the upslope flow off Lake Superior, so far affecting mainly southern Lake and east- central St. Louis counties. This area of stratus is slowly expanding, and where it spreads, will stall the radiational cooling. Otherwise, we are seeing warmer temperatures near both Lake Superior and some of our inland lakes. After the chilly start this morning, we should be able to burn off the stratus fairly early, and then we should see plenty of sunshine for the rest of the day. High temperatures should rise into the upper 50s near the lake to the low to mid 60s further inland. Easterly winds will become gusty this afternoon, particularly near Lake Superior where gusts of 15 to 25 mph are expected.

Tonight will not be as cool as this morning- the ridge of high pressure will slide east during the day today, allowing return flow to set up tonight. We are still expecting overnight lows in the mid 30s to low 40s, leading to another threat of frost, mainly for inland areas. During the day on Wednesday Southerly return flow will strengthen on the backside of the departing high pressure system, allowing afternoon temperatures to climb into the mid to upper 60s across the region, though we can still expect upper 50s along the North Shore. Clouds will gradually increase through the day ahead of an approaching upper level trough. Winds will shift to the southeast and become a bit breezier by the afternoon.

Precipitation chances finally return to the area Wednesday night into Thursday as a potent shortwave moves across the area from the southwest. Showers will spread from west to east across the Northland, mainly during the overnight hours, and continue through Thursday. The atmosphere remains quite dry in the lower levels, which may limit overall rainfall amounts, but a wetting rain of at least a tenth of an inch is possible, mainly for northern Minnesota. By Thursday night, the shower activity will exit, leaving us with mostly cloudy skies overnight.

Friday we will still be in that southerly return flow, which should help boost our temperatures into the 60s to near 70 nearly everywhere. We will likely still be under mostly cloudy skies, but no rain is currently expected.

Looking ahead to the upcoming weekend, temperatures will remain in the near to above normal category, with upper level ridging in place over the region. Highs by Sunday and Monday should once again reach the mid 60s to lower 70s, with the warmest temperatures across northwest Wisconsin. The forecast does remain a bit unsettled as additional weak disturbances move across the region. This will result in off and on chances for precipitation Saturday through Monday, though no significant widespread heavy rain or severe weather is anticipated at this time.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1225 AM CDT Tue Sep 22 2026

VFR conditions are expected at all terminals save for some fog at HIB tonight, which will lead to visibilities dipping to IFR. This should improve as temperatures rise in the morning. Winds will increase tomorrow to around 15 kts.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 319 AM CDT Tue Sep 22 2026

High pressure centered over eastern Ontario will maintain east/northeast winds over Lake Superior today and tomorrow. The strongest winds will be in the western arm and along the South Shore both days, where we expect sustained winds of 15 to 20 knots with gusts approaching 25 knots. A Small Craft Advisory has been issued for several hours this afternoon and early evening for these areas. Another round of hazardous conditions may develop again tomorrow, but for a shorter time frame and for a smaller area. Winds veer to the east to southeast Wednesday afternoon.

For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt.

FIRE WEATHER

Issued at 241 AM CDT Tue Sep 22 2026

Minimum relative humidity values will drop into the 35 to 45 percent range for the Wisconsin Pine Barrens, while remaining above 45 percent for the rest of northwest Wisconsin and all of northeast Minnesota. Easterly winds will gust to around 15 to 20 mph near Lake Superior, with lighter winds expected inland. Wednesday will see slightly higher humidity values. Rain chances return to the area Wednesday night into Thursday, though widespread significant wetting rains are not expected for most of the area.

See the Fire Weather Forecast product for a more thorough breakdown of fire weather conditions.

DLH WATCHES/WARNINGS/ADVISORIES

MN...Frost Advisory until 8 AM CDT this morning for MNZ010>012-018- 019-025-026-034>038. WI...Frost Advisory until 8 AM CDT this morning for WIZ001>004- 006>009. MARINE...Small Craft Advisory from 2 PM this afternoon to 10 PM CDT this evening for LSZ143>146-148-150.