Why does it rain and what's causing Michigan's storms to get stronger?

Extreme weather doesn’t fit neatly into the climate change models. One happens in an instant. The other is the makeup of decades of data. 

Experts like climatology professor Jeffrey Andresen at Michigan State University won’t say climate change caused any single extreme weather event. But the conditions created by warming trends can make it more likely that severe weather will occur.

"As the climate does change - usually it’s a type of gradual change - we increase our chance of probabilities of extreme or short-term storms," he said. 

Why does it rain?

To create rain, a region needs two things: a source of water and a way of lifting up that water. The Great Lakes has a comfortable supply of both. Most of the water vapor that eventually turns into rain in Michigan starts in the Gulf of Mexico and the Atlantic Ocean. 

It can come from other places too - like the surrounding lakes and plants from the heavy density of surrounding agriculture. 

Then, as the winds circulating around a low-pressure system moves in, they lift that vapor high enough into the atmosphere where it cools, condenses, and falls as water droplets. 

That's how you make rain.

What about Michigan's climate is changing?

But what happens if you ramp up the dosage of one of these ingredients? The Midwest has certainly seen more rain in the past few years. A report from the Great Lakes Integrated Sciences and Assessments found annual precipitation in the region has increased by 14% since 1951, with the greatest increase happening in the winters and springs.

Meanwhile, the NOAA data from the National Centers for Environmental Information calculate this is the second wettest five-year period in Great Lakes history. June 2021 was the 10th wettest month in Michigan history when an average of 4.9 inches fell on the state. Detroit recorded more than 6 inches in its historic June storm alone.

There’s a growing consensus that higher temperatures are the culprit behind the heavier amount of rain and snow. Warmer conditions can hold more moisture. Most residents may remember the relentless humidity in late June. As more vapor builds up, the chance for a larger storm increases. If the right wind conditions move in - as they did on June 25-26 of 2021 - all that moisture moves with it until it precipitates.

"The warmer air can hold more vapor, so there’s always more potential for extreme events," said Andresen. 

Ironically, the gradual intensification of agriculture in the Midwest may also be keeping Michigan from getting too hot. The Great Lakes may not suffer the same scorching heat inflicted on the western U.S. because all of the evaporation that plants are doing is sucking some of the energy out of the local system. If there’s less energy in the system - it can’t heat the surface as much.

Climate models predict that in the next 50 years, it will be two degrees warmer - which will contribute to 20% more precipitation, Andresen says.