Multiple US states in the northeast have entered a state of emergency after strong thunderstorms resulted in severe flooding this weekend.

At least one person has been killed by the extreme weather. The woman, in her 30s, was attempting to evacuate her Hudson Valley, New York home before being swept away by strong flood tides.

Officials in Orange County are among those to declare a state of emergency, several people are missing after the area received up to 20 cm of rainfall on Sunday.

Large boulders, dislodged by the rainfall, have fallen and hit homes in the county as flood waters rose to surround homes, trapping those who had yet to evacuate.

One expert flood researcher Tweeted on Sunday, suggesting that flooding in the northeast US could quickly become the worst flood event since Hurricane Ida in 2021.

The full extent of damages will become clearer once day breaks, though New York officials say the financial cost has already exceeded tens of millions of dollars.

Heavy rainfall continues today, having pushed north of New York towards Massachusetts and Connecticut.

Responsible for the extreme weather is a combination of warm, summer moisture mixing with cooler, unseasonable air over Ontario in the east of Canada. Creating instability and ripe conditions for thunderstorms.

Meanwhile, India has seen extreme rainfall stemming from a heavy monsoon resulting in widespread floods.