Cooler water temperatures on Lake Michigan
Cooler water temperatures could be coming to Lake Michigan today and for the next few days, all thanks to cold water upwelling. Cold water upwelling can occur at almost any time of the year, but we typically notice it during the summer, when everyone likes to cool off in the water.
This process can happen a couple different ways: from higher waves after a low pressure system moves through or a persistent wind out of the east. When we get those winds out the east, it actually pushes the warmer water right on the surface farther away from land and into the middle of the lake. When this happens, something has to replace that warmer water, so colder water has to come up from below. You can really see this in action when you take a look at buoy temperatures in the middle of the lake and on the shoreline. But, the chilly water moves pretty slow, and a noticeable difference may take a few days in some instances. We saw a case of upwelling not too long ago - take a look at the graph.
This is the water temperature of Lake Michigan during the middle of this month. Notice the sharp drop from 74 degrees to 59 degrees - this was caused by upwelling.
When those temps drop like this, it can catch swimmers and beachgoers off guard, and you could suffer cold water shock. When someone is going through cold shock, they can have trouble controlling their breathing - they can hyperventilate or feel like they are suffocating. Exposure to the cold water will also increase someone's heart rate and blood pressure, which increases the risk of heart failure or stroke. Even a person's ability to think clearly is impacted by the shock of cold water.
All of these factors involved drastically increases people's chances of drowning, so on days like today when upwelling is possible it is very important to stay safe and avoid getting in the water.
Luckily, it does look like the risk drops off as we move towards tomorrow and Wednesday, but it's still something to be aware of for the rest of the summer season.