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What is Summertime Lake Effect?

Here is an excellent example of summertime lake-effect or as some might refer to it “anti” lake-effect. That is because at this time of the year daytime air temperatures get much warmer than the adjacent water temperatures of the lakes. In conditionally unstable airmasses, the cooler lakes will suppress cloud growth as well as convection/thunderstorms. In fact, there is some truth to the comment that the lakes may actually protect areas downwind from severe weather in the summer.

In the main image above, you see a satellite image, which shows cloud free lakes. The important image is the first one below; those are radar echoes surrounding Lake Erie and the red blobs are thunderstorms, which are almost all completely over land. Notice the air temperatures are close to 90F in many areas while Lake Erie’s water temperatures are in the upper 70s to low 80s.

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Note however that not all thunderstorms miss the lakes or weaken as they cross the lakes. If the thunderstorm development is not “surface-based” but is forced from other features like upper level jets etc. then the action can move right across the cooler bodies of water and hammer downwind locations. BTW, at this time of the year, as we get to sunset, land temperatures cool down and the lakes do not have as much impact on dampening storms, so you will see more activity develop over the lakes going into the night time hours. As we head into August, the overnight air temperatures get cooler than lake temps and we actually can get thunderstorms that develop over the lakes, called nocturnal storms. That is the beginning of the lake-effect season we are more familiar with. It is AMAZING out there, enjoy !!

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5 Comments


  1. Hi Tom,
    I’m from the Buffalo, NY area, like you are. It’s been very dry this summer. It seems as if every time a good chance of rain comes over Michigan, it breaks down before getting here. Do you know why? The last few days rain has come, due to the southerly winds. Thanks.

  2. Excellent question Robert, the cooler waters of the Great Lakes do suppress some convection during the summer. However, they are all warmer than they have been on average and over the past five years so I would not tie the dry conditions across the Great Lakes to lake temperatures. It has a lot more to do with the large scale weather pattern across the US.

  3. What an interesting topic and explanation. I was just thinking… why it has been so dry in Northern MI this year? Believe it or not, I wondered if the cooler waters of the Great Lakes had something to do with it. Never stop learning y’all!

    1. Ahh yes, Lake Superior boasts some of the coldest waters of any Great Lake in the summer and as a result you end up with much less diurnal (during the day) cloud cover. Go to my Facebook page and I will post an image of Superior today for you, it doesn’t seem to let me do that on this page, sorry.