Hurricane Florence: How much would its rainfall have raised the level of Lake Michigan?

Posted at 9:26 PM, Sep 18, 2018
and last updated 2018-09-18 22:22:29-04

WEST MICHIGAN — I remember last year in 2017 some 56 inches of rain from Harvey in southeast Texas fell in spots. Absolutely incredible! I also remember talking about how high that would have raised the level of Lake Michigan. Now about a year later, we are at the same crossroads. Hurricane Florence dropped about eight trillion gallons of water across the state of North Carolina from September 13 through September 17. Count ’em…that’s 12 zeros! How much would that have raised the level of Lake Michigan? Great question.

I should note that Lake Michigan and Lake Huron are part of the same basin. They connect through the Straights of Mackinac and are part of the same basin. That said, it takes 790 billion gallons of water to raise the basin only one inch in height. Remember billion is nine zeros (790,000,000,000). With that in mind, if we take eight trillion and divide it by 790 billion, we get about 10.1. That means the eight trillion gallons of rain that fell across North Carolina from Hurricane Florence would have raised Lake Michigan/Huron about 10.1 inches in height! See graphic below.

Here’s another way to look at it. If we strip out Lake Huron and just consider Lake Michigan, it takes about 390 billion gallons of water to raise (only) Lake Michigan one inch. That same eight trillion gallons of water would have raised Lake Michigan 20.5 inches. More than a foot and a half! These numbers are staggering. You can imagine the catastrophic flooding that North Carolina is experiencing now. The map below shows approximate rainfall totals across the state. Thanks to the National Weather Service for the map and numbers. Wilmington alone saw between 30 and 50 inches of rain from Florence! I would expect it will be weeks before the water completely recedes and clean up can begin for some. In fact, some rescues are still being conducted.

Here in West Michigan we will increase our chances for showers and thunderstorms this week, with cooler weather to follow for the weekend. Get the complete forecast at Make sure to “like” my Kevin Craig FOX 17 Facebook page for more facts, viewer photos, behind-the-scene stuff, and weather forecasts!