It’s been a crazy couple of days here in the Greater St. Louis area as historic flash flooding has overwhelmed roadways, swamped cars, and caused a lot of damage to homes and businesses. By historic, I mean this was the biggest rain event this region has ever seen since records of such things exist starting in 1874.

According to the National Weather Service, in just six hours, the rainfall total surpassed the previous record set in a 24-hour period in 1915. To put it in a slightly different perspective, the St. Louis area received approximately 25% of its normal annual rainfall total in something like twelve hours, and closer to a third in some areas. It’s a hot mess.

Now, let me reassure you that though my suburban town did receive impressive rain totals and is in some places dealing with damage from the flood waters, my personal home is relatively elevated and has remained dry. I’m certainly very grateful for that. Other than having to alter schedules and commutes, my family hasn’t been particularly affected by the downpour.

Prior to the deluge, we St. Louisans had been experiencing a stretch of drought and we needed the rain, so we were more or less delighted when Monday brought us cloudy skies and occasional drizzles with the promise of a nice overnight thunderstorm. We just hadn’t anticipated so much rain so quickly.

It’s not that our weather forecasters hadn’t mentioned the possibility of a lot of precipitation and maybe even some flash flooding. We all accepted, I think, that it wasn’t going to be an ideal night to tent camp in a creek bed. But it’s not easy to anticipate an event that, to the best of our knowledge, has never happened before.

Even with all their university degrees, computer models, and fancy greenscreen maps, meteorologists have a pretty tough audience to try to reach. It’s just that they deal in probabilities and sometimes, the most probable thing that might happen, isn’t the thing that happens. The last highly anticipated St. Louis snow-pocalypse, for example, yielded less than an inch of light dusting. A little flash flood warning wasn’t going to scare us much.

Now if the meteorologists had run their prognostication by a “jury of philosophical counselors” consisting of at least twelve leeches, then that might’ve caught our attention. And if 19^th century English physician and leech enthusiast George Merryweather had gotten his way, that might’ve been what happened.

As a practicing physician in the era of physicians not always knowing what they were doing, Dr. Merryweather spent a lot more time than the average non-physician thinking about leeches. One thing he observed was that their behavior tended to change with the weather. He wasn’t the first to realize this. For a long time, people who had nothing better to do had noted that leeches rise out of the water when a storm is coming and roll themselves into a ball when the storm is at hand.

But amazingly, Dr. Merryweather was the first to design a leech-powered weather predicting device. He called it the “Atmospheric Electromagnetic Telegraph, Conducted by Animal Instinct,” which he then shortened to the “Tempest Prognosticator.”

It was an impressive apparatus, consisting of a circle of twelve glass jars arranged around a large metal ball. Each jar contained a little bit of rain water, a leech, and a whale bone striker at the top, which when bumped by a leech climbing into the bottleneck in anticipation of a coming storm, would strike the metal ball and give a warning of impending inclement weather. When enough of Merryweather’s slimy little philosophical counselors sounded the alarm, he knew a storm was on its way.

The really weird part is that it worked, kind of. Or at least it worked as well as other weather predicting equipment of its day. It had limitations, of course. The leeches, who aren’t known to be great communicators, weren’t forthcoming with the direction of a storm, and to be honest, probably wouldn’t have predicted record-breaking flash flooding any better than today’s computer models could.

In the end, Dr. Merryweather’s invention was not adopted as the gold standard of weather prediction he believed it would be. The tempest prognosticator was expensive and required some upkeep as water needed to be changed every week and the jury wanted feeding once in a while. Also, outside of the 19^th century medical profession, most people agree leeches are slimy and gross.

But I’m picturing the article headline that might have been: “Leeches Predict Historic St. Louis Rain-Pocalypse.” Something like that would have lit up everyone’s social media feeds and gotten a fair number of clicks, I bet.