Like the first snowfall of winter, the Mayfly "hatch" is a hard-to-miss marker of the summer season's arrival around the Midwest, especially on major lakes and rivers such as the Mississippi. The bugs people have seen the past few days are just the final, very brief stage of a life cycle that begins on river and lake bottoms. The pictures below were taken by Jason Matthew in Burlington, Iowa the night of July 2nd.
The burrowing mayfly common along the Mississippi, builds a hole in the river bottom and lives most of its life there, usually emerging in mass in late spring and early summer to mate, lay eggs, and die in a frantic dramatic swarm that lasts a day or two. They need oxygenated water and a healthy river to survive their larval stage, so their emergence should be taken as a positive sign that the water they originate from is in good shape.
This year's hatches have again created localized piles of bug corpses which in some years are so substantial they require the help of snowplows to clear bridges and waterfront highways. That's not an urban myth, it's actually happened! Having lived along the Mississippi for nearly 30 years, I can remember one hatch that was so bad the roads were actually slick from Mayfly remains. The Mayfly is also known as the fishfly in some circles, especially the ones I was familiar with in Dubuque. The hatch usually takes place on nights when it's warm and very muggy.
Often times the hatch involves millions of bugs and is so dense that our highly sensitive Doppler radars can easily detect the swarms as they emerge from the water. The image below is from the NWS in La Crosse, Wisconsin.
Here's a huge swarm coming off Lake Erie
Speaking of swarming, a heat wave is expected to build over the Plains early next week and eventually creep northeast toward the central Midwest. Fortunately, we'll never get into the true heart of it but there's likely to be several days late in the coming week and weekend where heat index values could over 100. Best chances for this occurring is during the period the 9th-13th. The GFS is the most bulliish with a couple days of heat index values pushing 105 It's a little early to confirm the trend but it falls in the most favored climatalogical time of year for both heat and high dew points. I could see it!
Last but not least, I came across a tweet from the NWS on the impact some of our founding father's had on the field of meteorology. These guys were way ahead of their time in so many ways. Here's to their invaluable contributions to science and mankind as a whole.
Here's hoping your holiday weekend is going well. Until next time, roll weather...TS