Isaac unleashed flooding rain on eastern and southern Puerto Rico late this week, prompting the U.S. territory to open 428 emergency shelters.
More than 4,000 people were without power and more than 3,000 without water after the floods.
"Training-effect rain and thunderstorms were blasting Puerto Rico like a giant fire hose during Friday," Expert Senior Meteorologist Alex Sosnowski said.
Some roads have been blocked by mudslides and at least one bridge was reported washed out along the southern part of the island.
Governor Luis Fortuno announced it was safe for people to go to work on Thursday, but warned against nearing beaches and swollen rivers.
Travel was interrupted to and from Puerto Rico's main international airport as some airlines canceled flights, though the airport itself remained open.
Severe thunderstorms with the risk of a few tornadoes will advance eastward across the northern Plains and Upper Midwest into Friday.
A dangerous outbreak of severe storms will strike the northern High Plains and Canadian Prairies on Wednesday.
Join us on Thursday for AccuWeather LIVE as we will discuss the debate of climate change and hurricane frequency and the top five things you need to know about summer weather.
A hot and humid weekend is shaping up for Chicagoland just in time for the official start of summer, while severe thunderstorms fire nearby to the north.
A tornado touched down at Denver International Airport as a severe weather system moved through the area.
A brief synopsis of the top five worst weather events of last summer.
Philadelphia, PA (1994)
Strong thunderstorm winds blew off a large section of a hanger roof and also damaged two aircraft.
Central Illinois (1964)
19th-20th) Hail as large as grapefruits battered more than 50 counties, causing crop and property damage totalling $9.2 million.
3-4" rains common across the state.