textproduct: Marquette

KEY MESSAGES

- The warmest airmass of the season so far will impact the UP with highs in the 90s through Tuesday. High dewpoints and poor overnight recoveries will increase cumulative impacts. So, an Extreme Heat Warning has been issued for all of Upper Michigan today. People sensitive to heat should make preparations for these conditions.

UPDATE

Issued at 24x AM EDT Mon Jul 13 2026

The going forecast remains mostly on track this morning. Thunderstorms are ongoing over the eastern third of the CWA, but as those depart throughout the early morning hours, precipitation is unlikely through the midweek period and the weather impacts are confined to the oppressive heat today and tomorrow and gusty marine winds today.

Today and Tomorrow Heat: The heat comes to a head the next couple of days as the upper level ridge extends overhead from the west. The well-advertised near-record ridge at 500mb will threaten many all- time record highs today before even considering humidity. Even if the NBM is right and dew points in the interior mix down to around 60 degrees (a solution that puts the NBM around the 25th percentile of guidance), heat indices will still reach the triple digits for several hours for most of the UP today. The NBM shows WFO MQT reaching 99 degrees, which would place today in a 4-way tie for the all-time record (period of record since 1961). If downsloping can get the shoreline to 100 degrees, it will be only the 27th time 100 degrees has been recorded since the 1860s (including times with less reliable instrumentation and siting). The Ironwood WWTP site has not recorded a 100 degree temperature since the 1940s, while the Iron Mountain WWTP site has only reached 100 3 times since the 1940s (the IMT ASOS has never recorded 100 degrees F since it was installed in 1996). All of this to say, the level of heat today will likely (50+%) be on the level that most Yoopers would have to leave the UP to experience in their lifetimes. Overnight lows tonight only look to fall to the low to mid 70s, providing little relief for those without air conditioning. Tuesday will remain hot, but the NBM only highlights triple digit heat for the south-central while the remainder of the UP "cools" to the mid-90s to upper 80s. While there is still a disappointing amount of spread in the models for Wednesday and beyond, the general understanding is that troughing over eastern Canada will be deep enough to cause 500mb heights to fall sufficiently that the highs for Wednesday and beyond would be described as "above normal" and not "extreme".

Gusty Marine Winds: With the RAP analyzing a near-1000 mb low passing through Hudson Bay today, the pressure gradient squeezes to 20 mb from Hudson Bay to central Lake Michigan. This in addition to mixing gustier winds at the midlevels to the surface will drive gusts in excess of 25 mph for the Keweenaw and for some shores along Lake Superior. Wave heights this evening north of the Keweenaw will be well in excess of 5 feet around the boundary between the nearshore waters and the open lake (5 miles from shore). This may make conditions hazardous for small craft for those who are trying to escape the heat by going on the water.

DISCUSSION

Issued at 401 PM EDT Sun Jul 12 2026 Amended at 24x AM EDT Mon Jul 13 2026

There will be little temperature recovery even this morning with lows only decreasing into the 60s and 70s. With today being the hottest day of this heat wave, an Extreme Heat Warning has been issued for all of Upper Michigan as heat indices soar into the 105 to 110 degree range. By Tuesday, the extreme heat threat shifts to mainly the southeast. Therefore, the extreme heat warning will likely be continued for Menominee and Delta Counties with future forecast issuances. Meanwhile, the remainder of the forecast area will likely fall under a heat advisory on Tuesday unless future model runs change drastically.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 126 AM EDT Mon Jul 13 2026

VFR conditions are expected to dominate today into this evening as high pressure ridging keeps skies SKC. While some low-level turbulence could be seen over the terminals early this morning and again after sunset this evening, no LLWS is expected save for potentially a small chance for marginal LLWS near KSAW a couple of hours right before sunrise. Expect gusty W'rly winds throughout the day today, although the lake breeze may turn the winds NE/ENE'rly over at KSAW this afternoon.

MARINE

Issued at 401 PM EDT Sun Jul 12 2026 Amended at 24x AM EDT Mon Jul 13 2026

Southwesterly winds have increased to 25 to 30 kt across the western half of the lake and over the central as pressure gradient tightens while a strong low moves along the high pressure ridge. By tonight, southwesterly winds will approach gale force (20% chance) before gradually diminishing Tuesday morning and below 20 kts by Tuesday afternoon.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Extreme Heat Warning from noon EDT /11 AM CDT/ today to 10 PM EDT /9 PM CDT/ this evening for MIZ001>007-009>014-084- 085.

Lake Superior... None. Lake Michigan... None.