This radar image was obtained by the National Weather Service Weather Forecast Office in La Crosse. The area depicted is where the states of Minnesota, Wisconsin, and Iowa meet.

A mayfly hatch along the Mississippi River was caught on Doppler radar out of NWS La Crosse this evening. The radar view below shows an image at 9:13 p.m. CDT on Saturday, May 29, 2010. The bugs are showing up as bright pink, purple, and white colors along the Mississippi River mainly south of La Crosse, WI. After the bugs hatch off the water and river areas, they are caught in the south-southeast winds while airborne for about 10-20 minutes.

Link, via.