The main threats over the weekend will be damaging winds gusting up to 60 mph, large hail up to the size of quarters and heavy rainfall that could result in isolated flooding.

Severe thunderstorms and tornado watches are in place on Tuesday, with 40 million Americans on alert for strong winds, large hail and flash flooding.

Those with outdoor plans this Memorial Day weekend should have ways to receive warnings and stay tuned to changing weather conditions.

Tornado sirens are usually the telltale sign to take cover during severe weather. In St. Louis, tornado sirens didn't go off during a deadly tornado.

Millions from Oklahoma, Kansas, Missouri and Nebraska are under severe weather threat. In St. Louis, Missouri, families are cleaning up after devastating storms in recent days. NBC News’ Shaquille Brewster is there.

Severe weather conditions are possible in areas of Colorado’s Eastern Plains on Friday evening, with the potential of bringing up to apple-sized hail, wind gusts and tornadoes.

The IMD has issued red and orange alerts for Maharashtra and Goa as a depression forms over the Arabian Sea. Heavy rain, gusty winds, and traffic disruptions are expected.

A severe thunderstorm warning was issued by the National Weather Service in Norman at 08:45 a.m. on Thursday, May 22.