Stalled systems and moisture pouring in from the Gulf of Mexico were leading to thunderstorms and the chance of heavy rainfall in 20 states.
The National Weather Service (NWS) has forecast excessive rainfall until Tuesday in Texas, through parts of the southeast, and up the eastern seaboard as far as Maine.
Scattered to numerous flash floods are possible from the Gulf Coast to the Northeast.
“Mother Nature has turned up the heat this Labor Day as record-breaking temperatures continue across a large region extending from California to the northern/central High Plains,” a NWS forecast added.
Highs are expected to reach into the upper-90s (degrees Fahrenheit) and triple digits, with 110s probable throughout the Southwest and central valleys of California.
In some areas, the ground is already saturated from this weekend including northwest Georgia where downpours left some communities underwater after localized rain of up to 12 inches (30cm).
Georgia Governor Brian Kemp declared a state of emergency in Chattooga and Floyd Counties following severe flooding. The city of Summerville advised residents who use the city’s water utility services to boil water prior to drinking, cooking or preparing baby food due to flash flooding at the Raccoon Creek Filter plant. It wasn’t clear on Monday how long it would take to make repairs to the system.
Georgia, Alabama, Tennessee, North Carolina, South Carolina, Kentucky, Virginia and West Virginia were under flash flood watches through Monday evening, NWS reported.
Chances for heavy rain also extended along the I-95 corridor from Washington DC to Providence, Rhode Island through this week.
The United States faces greater risk of “flashier” floods as the climate crisis worsens.
The country will experience more frequent and more extreme flash flood events by the end of the century if greenhouse gas emissions rise unabated, according to a study published in the journal Communications Earth and Environment in April.
Recent incidences of flash flooding have proven to be deadly. This summer, rapid onset floodwaters in eastern Kentucky killed at least 38 people, with countless others left needing to rebuild destroyed homes and towns.
AP contributed to this report