It's actaully very rare to get an all day rain event in August. Usually it rains for a few hours, or even half a day. But TWO days of rain and drizzle are very rare.
The storm system responsible for this mess had a central pressure as strong as Tropical Storm Gert. The only difference is that our storm was dozens of times larger. The combination of the strength of this storm and its interaction with abnormally warm waters over the Gulf Stream setup a conveyor belt of tropical moisture streaming directly towards the tri-state.
The hardest hit areas in Connecticut were Debry, Milford and Shelton with radar estimates between 4" and 6"! No wonder the CT Post Mall flooded! Here is video of th flooding in Derby where a section of Rt 34 had to be closed due to flooding.
But we didn't even get the worst of the rain. NYC needed scuba gear to get around. In Central Park, 4.87″ of rain fell by 7pm. That’s enough to make Sunday the rainiest single August day in NYC since 1869, the ninth wettest overall. Officially, Sunday was the rainiest day ever recorded at JFK (7.72″ as of 7pm, beating June 30, 1984 by more than an inch and a half), with rain falling at nearly three inches per hour at one point. Unofficially, storm spotters recorded an amazing 10.20″ in Lido Beach on Long Island. I was in Staten Island for a wedding this weekend and I can confirm in my expert meterorological opinion that is was miserable.
Here are some of the rainfall totals reported from the National Weather Service. Windsor Locks had the lowest amount at 1.50" in 48 hours.