Crozet Weather Almanac: July 2014


Thunderstorm or Just Bugs?

By Roscoe Shaw and Heidi Sonen

July 2014 Temperatures and Rainfall
July 2014 Temperatures and Rainfall

Way back toward the middle of last century when Heidi and I were young loves, we decided to go to Kansas City for a romantic getaway.  What happened that hot July night was right out of a 1980s horror flick.  We were engulfed by a swarm of mayflies.

Driving down Interstate 29 along the Missouri River,  suddenly we heard what sounded like big raindrops.  But quickly, our windshield became smeared with bugs.  Not just a little bit, either.  Heidi turned on the wipers and fluid and but we had no chance.  We had to pull over.  We looked for something to clean the windshield and then drove more.

We drove slower but very soon, we were completely slimed again as we committed mass murder of millions of mayflies.  We had nothing left to clean the windows with.  Eventually, we made it to a gas station where other cars were trying to clear their view, too.  We stocked up on liquid and paper towels and braved the road again.

Did I mention the dead bug-fest on a hot summer night was gross?  Really, really gross.

Suddenly, we broke out of the bugs and resumed clear sailing.  The next day, we washed my old Subaru, something I almost never do.  The green car was completely brown on the windward side from a fresh thick coat of dead bugs.  We didn’t dare touch it.

Mayflies tend to hatch all at once in the heat near the water.  They only live a day or two, either dying by Subaru or natural causes.

Mayflies on radar
Mayflies on radar

Bugs on Radar

My first job out of graduate school was as a tornado chaser.  That sounds crazy but most of the time, it was rather boring and methodical research.  The NEXRAD Doppler radar system that we now rely on was brand new.   Our job was to drive into storms so that we could match what the new radars indicated versus what was actually occurring on the ground.

One thing we noticed was that we often saw minor but very real radar echoes in clear skies during summer.  Frequently, storms erupted in these areas later in the afternoon.  Eventually, we realized that we were seeing bugs on radar that converged into groups due to wind flows.  These same convergence zones later produced thunderstorms.

Mayflies can produce radar echoes as strong as a thunderstorm.  Recently, radar near LaCrosse, Wisconsin (pictured) recorded bug echoes of 40 DBZ which is the same as a  substantial summer thunderstorm.

July Recap

The first half of July was normal with highs up to 94 degrees and some typical thunderstorms.  But the second half of the month turned very cool and dry.  We had lows in  the 50s six times and our lowest of 51 was just two degrees off the all time July low of 49 set back in 1913 and tied in 2002.

All seven months this year have been cooler than normal.  That wasn’t much fun in January but most of us like it in July.


Spring was wet so our water tables are in good shape but late July was quite dry.  Of course, at this time of year, amounts vary quite a bit from place to place.  Our house seems to have gotten the least rain.  Average July rain is nearly five inches.

  • Mint Springs 1.44”
  • Old Trail  2.57”
  • Yancey Mills  2.44”
  • Greenwood  2.66”
  • Univ of VA  2.78”
  • Waynesboro  4.19”
  • Whitehall 2.20”
  • CHO Airport  3.05”
  • Nellysford 2.67”


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