textproduct: Duluth

KEY MESSAGES

- A Frost Advisory is in effect early this morning for the Borderlands

- Persistent northeasterly winds will keep the threat for rip currents going at Twin Port beaches today and may linger into mid-week as well. They will also create hazardous conditions on Lake Superior through Tuesday.

- Widespread frost and perhaps some areas of freeze are forecast for tonight into Tuesday morning. Additional chilly nights with the potential for frost are expected Tuesday night into Wednesday.

- Low chances for rainfall through the forecast period.

DISCUSSION

Issued at 231 AM CDT Mon Sep 21 2026

Early this morning, high pressure over northwestern Ontario is keeping our weather generally dry and cool. Between this high pressure and lower pressure to our south there is a relatively tight pressure gradient, which is maintaining breezy northeast winds, particularly near Lake Superior. Drier air is filtering into the area at low levels, but mid and high clouds have spread across the area from the low pressure system to the south. Temperatures dropping to overnight lows into the mid 30s prompted a Frost Advisory through 8 AM for Koochiching, North St. Louis, and northern Cook and Lake counties. Today, we expect the northeast winds to slowly decrease as the gradient weakens, and clouds will gradually clear from northwest to southeast during the daytime.

Tonight into Tuesday morning is likely to be our coldest night of the week. With the Canadian high settling nearly overhead, mostly clear or clear skies and light winds will set the stage for excellent radiational cooling. Lows are forecast to plummet into the 30s for most inland areas, while lakeshore communities remain slightly warmer in the 40s. A widespread frost is highly likely across the Northland, and some locations north of the Iron Range could see temperatures dip below freezing. Additional frost or freeze headlines will likely be needed for tonight into Tuesday morning.

On Tuesday, the high pressure center will begin drifting toward the east, causing our winds to veer southeasterly. This return flow marks the beginning of a gradual warming trend that will carry us through the remainder of the week. Afternoon highs on Tuesday will rebound comfortably into the 60s, though the onshore flow will keep the North Shore a bit cooler in the upper 50s. Another chilly night is expected Tuesday night, bringing yet another chance for patchy frost inland.

Upper level ridging will build across the Upper Midwest for the middle and later part of the work week. A shortwave riding over the top of the ridge brings a chance for showers Wednesday night into Thursday, but dry low levels will limit widespread rainfall. Otherwise, the ridging aloft will provide generally dry and quiet weather with temperatures slowly rising into the weekend. Highs will reach the mid 60s to lower 70s for Friday and Saturday. Precipitation chances remain quite low and spotty heading into the weekend even as the ridging eventually slides eastward.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 622 AM CDT Mon Sep 21 2026

Predominantly VFR conditions are expected for this TAF period. KDLH has some stratus this morning, and KHIB and KINL have MVFR fog. Both sites should improve back to VFR by 14z this morning. KDLH will have east winds around 10 knots, but all other terminals will have winds of less than 10 kts. VFR conditions are then expected through most of the remainder of the TAF period. Fog is possible again tonight, especially for KHIB, and have included some MVFR visibilities beginning around 09z.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 231 AM CDT Mon Sep 21 2026

Hazardous conditions will persist across western Lake Superior through Tuesday, due to strong gusty winds caused by a tight pressure gradient. East to northeast winds of 10 to 15 knots with gusts reaching 25 knots are expected today, highest in the western arm during the afternoon and early evening. Waves will build to 2 to 4 feet. A Small Craft Advisory has been issued for today and this evening. Winds and waves will both relax overnight tonight. Northeast wind gusts to 25 knots will redevelop by Tuesday afternoon, which may require an additional Small Craft Advisory.

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

FIRE WEATHER

Issued at 231 AM CDT Mon Sep 21 2026

Winds continue to be the main concern today and tomorrow, especially near Lake Superior. Gusts up to 20 mph will be possible this afternoon and early evening before diminishing during the evening. Minimum RH values are expected to remain above 50%. Afternoon minimum RH values of 40-55% are expected for Tuesday and Wednesday. Values may fall into the 35-45% range both days across the Wisconsin Pine Barrens. The next chance for light rainfall arrives late Wednesday into Thursday, though significant wetting rain is unlikely.

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. Beach Hazards Statement from 10 AM CDT this morning through this evening for MNZ037. WI...Beach Hazards Statement from 10 AM CDT this morning through this evening for WIZ001. MARINE...Small Craft Advisory from noon today to 10 PM CDT this evening for LSZ143>148-150.