Surface water temperatures at Michigan’s shoreline communities have seen a real roller coaster this year.  Heading into the weekend, the roller coaster is taking a headlong plunge in some coastal areas. And seemingly in the blink of an eye, did another abrupt changeover and went back up to near normal overnight. In a couple of areas, Lake Michigan's surface water temperatures saw a better than a 30-degree drop and then jumped back up over two days. Last month, surface water temperatures in many Great Lakes communities were well above normal, some into record-high levels. That was due in large part to that long string of 90-degree days that kept air conditions running on high.

In this situation, it’s a natural occurrence. Some refer to it as the lake “turning over”. Weather geeks call it an “upwelling”. We normally see that happening along the southern and central shoreline of Lake Michigan. Warmer surface waters along the Lake Michigan shoreline get displaced by colder water from deeper areas offshore.  It can happen fast. One moment the water temperature is in the mid to upper 70’s. Within just a few hours it drops into the 60’s, then the 50’s, and in some cases even into the 40’s and in extreme cases into the 30’s. Like this week. That can change a fun day at the beach into something painful, and even dangerous. Michigan State University’s Coastwatch website was showing  Lake Michigan surface water temperatures between South Haven and Saugatuck in the upper 30’s for about 24 hours through mid-afternoon yesterday. And just as quickly, moved back up into the mid 60’s by this morning. A little further north along the shoreline, surface water temperatures at Muskegon are now in the mid 50’s.

Boaters and swimmers alike need to be aware of conditions before venturing out. A boating accident that leads to someone going overboard into water that cold is immediately life-threatening. Kids often don’t pay as much attention to water temperatures and could be caught off guard jumping in at the beach.

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