Great Lakes Water Temperature by Month: Lake Michigan, Erie & 18 Beach Towns

Quick answer: Lake Erie is the warmest Great Lake, 75 °F lake-wide in August; Lake Ontario reaches 72 °F, Lake Michigan 71 °F, Lake Huron 69 °F and Lake Superior only 61 °F. Off the southern Lake Michigan beaches (Chicago, St. Joseph, South Haven) it averages 71–73 °F in July and August. From January to April every lake is below 45 °F.

How to use it

Pick a lake for its lake-wide average, or one of 18 beach towns (Chicago, Milwaukee, Grand Haven, Muskegon, Traverse City, Duluth, Cleveland, Erie, Buffalo, Rochester and more) for the water off its beach, and the month you go; the month you are in is filled in. The answer is the water’s average that month and where it sits against NOAA’s comfortable range, with most days’ range and the warmest and coolest months; a beach town also shows its lake as a whole for the same month. Below it: the twelve months as bars, every beach town and every lake ranked for your month, and, when NOAA has it, the latest day’s reading. Switch to °C if you like.

Where the numbers come from

NOAA’s Great Lakes Environmental Research Laboratory (GLERL) maps the lakes every day. In its own words: “The Great Lakes Surface Environmental Analysis (GLSEA) is a digital map of the Great Lakes surface water temperature and ice cover which is produced daily.” and “Lake surface temperatures are updated daily with information from the cloud-free portions of the previous day’s satellite imagery (+/- 10 days). If no satellite imagery is available, a smoothing algorithm is applied.” For each lake the tool reads GLERL’s daily lake-wide average for every day from 2007 to 2025. For each beach town it takes the grid cell (about 1.4 km wide) nearest the town in its Great Lake, never a harbour lake such as Muskegon Lake or Presque Isle Bay, and reads every 4th day of the same years: 135 to 148 days for each calendar month, averaged, with the middle 80% as “most days”. It is the surface of the lake off the beach, not the water at your feet. NOAA’s Coastal Water Temperature Guide says “There’s no real optimal temperature, but many people feel “comfortable” swimming in water that is 70° to 78° Fahrenheit”, and warns that “even in the summer, prolonged immersion in water temperatures below 70° Fahrenheit can produce hypothermia.”

In °F, each month’s average from 2007 to 2025: the six lakes lake-wide, then the water off each beach town. Lake Erie is the warmest: 74 °F lake-wide in July, 75 °F in August and still 71 °F in September. Lake Ontario reaches 70 °F in July and 72 °F in August; Lake Michigan reaches 71 °F in August only. Lake Huron peaks at 69 °F and Lake Superior at 61 °F, both in August, so neither averages inside NOAA’s comfortable range in any month. Lake St. Clair, between Huron and Erie, is 74 °F in July and August.

The water off a beach town is usually warmer than its lake as a whole in summer. Off Chicago, Michigan City, St. Joseph and South Haven, Lake Michigan averages 71–74 °F in July and August, when the lake as a whole averages 67 °F and 71 °F. Further north it is cooler: Ludington and Milwaukee reach 70 °F in August only. On Lake Superior, Duluth and Marquette peak at 66 °F in August. On Lake Erie, Cleveland is the warmest town here, 76 °F in July and August, and Cleveland, Erie and Buffalo all stay at 71–72 °F in September.

Spring is slow and fall is kind. In May Lake Erie is 52 °F and Lake Michigan 44 °F; in June Lake Michigan is still 56 °F. September holds: Lake Michigan averages 67 °F, the same as in July.

Why your beach can be far colder than the average

A monthly average hides the days the water turns cold overnight. GLERL explains: “Coastal upwelling in lakes occurs when persistent winds move warm water away from the coast, and move cold water from the bottom up to the surface.” The National Weather Service’s Northern Indiana office described one on southern Lake Michigan in August 2006: “Upwelling is a process by which offshore winds push surface water away from shore, allowing cold lake water to rise up to the surface from beneath.” and “The onset of upwelling can occur very quickly, with lake temperatures falling 20 to 30 degrees in just a few days!” Its example: “on Monday August 7th both Warren Dunes State Park and Silver Beach County Park reported lake temperatures of 75 and 76 respectively. Just two days later on Wednesday August 9th, Warren Dunes was down to 55 and Silver Beach down to 49 degrees.” Silver Beach County Park is in St. Joseph, Michigan, where the August average here is 73 °F. Read the latest day’s reading above before you swim.

Worked examples

Lake Michigan in August. The lake averages 71 °F, its warmest month and just inside NOAA’s 70–78 °F comfortable range; most August days 67–74 °F.

Chicago in July. Off North Avenue Beach Lake Michigan averages 71 °F, inside the comfortable range; the lake as a whole averages 67 °F.

Grand Haven in June. 61 °F: the beach season starts cold. July averages 70 °F and August 72 °F.

Lake Superior in August. The lake averages 61 °F, its warmest month, below the 70 °F under which NOAA warns prolonged immersion can bring on hypothermia.

Duluth in August. 66 °F off Park Point, five degrees warmer than Lake Superior as a whole (61 °F), and still under the comfortable range.

Cleveland in September. Lake Erie averages 72 °F off the city, still inside the comfortable range; by October it is 62 °F.

Common mistakes

• Reading a lake-wide average as the water at your beach. In July Lake Michigan as a whole averages 67 °F, and 71 °F off Chicago.
• Expecting June to be swimmable. Lake Michigan averages 56 °F in June, and no beach town here averages 70 °F before July.
• Trusting the average after a windy week. Upwelling can drop the water at a beach by 20 to 30 degrees in a few days (see above).
• Treating Lake Superior like the others. It never averages above 61 °F lake-wide, and Duluth and Marquette peak at 66 °F.
• Reading a warm May afternoon for the water. In May Lake Michigan averages 44 °F and Lake Superior 38 °F, whatever the air feels like.

Plan the rest of the trip

Read whether Lake Erie is always cold, whether Lake Erie is safe to swim in summer, whether Lake Erie freezes, and what to do in South Haven, Traverse City and Chicago. Heading for salt water instead? Water Temperature by Month has the same record for 52 ocean beaches, and the Road Trip Cost Calculator prices the drive to the lake.