Tornadoes by the numbers: Damage reported across 14 states

A powerful storm system unleashed violent tornadoes and severe thunderstorms across the United States last weekend, killing more than two dozen people.

President Joe Biden has declared swaths of the country major disaster areas, freeing up federal funds and resources for recovery.

"While we are still assessing the full extent of the damage, we know families across America are mourning the loss of loved ones, desperately waiting for news of others fighting for their lives, and sorting through the rubble of their homes and businesses," Biden said in a statement on Sunday.

Here's a look at the extent of the storms so far.

81 tornadoes across 14 states

The National Weather Service has confirmed at least 81 tornadoes touched down in 14 states on March 31 and April 1. That number is expected to rise as surveys continue.

It's the largest single tornado outbreak to hit the U.S. in a year, since the one that spawned 140 twisters in southeastern states, from Texas to Maryland, on April 12-13, 2020.

170 mph winds

The National Weather Service currently uses the Enhanced Fujita scale to rate tornado intensity based on wind speeds and the severity of the damage caused. The scale has six intensity categories from zero to five (EF0, EF1, EF2, EF3, EF4 and EF5), representing increasing wind speeds and degrees of damage. There is also an unknown category (EFU) for tornadoes that cannot be rated due to a lack of evidence.

There were at least nine EF3s confirmed in five states -- Arkansas, Illinois, Indiana, Tennessee and Delaware -- on March 31 and April 1. EF3s have wind speeds ranging from 136 to 165 mph and typically cause severe damage.

The EF3 in Delaware had winds up to 140 mph and was on the ground for 20 minutes, covering more than 14 miles and growing to a maximum width of 700 yards. It's the widest tornado on record for the state.

There was one EF4 confirmed in Iowa on March 31, with winds up to 170 mph. It was on the ground for almost 50 minutes, growing to a maximum of 600 yards and covering an unknown number of miles. EF4s have wind speeds ranging from 166 to 200 mph and typically cause devastating damage.

32 fatalities

At least 32 people have died nationwide as a result of the storms on March 31 and April 1, according to a tally by The Associated Press.

The dead included at least nine in one Tennessee county. Other deaths were reported in Indiana, Illinois, Arkansas, Alabama, Mississippi and Delaware.

730,000 customers without power

More than 730,000 customers across five states were experiencing power outages in the U.S. on April 1 as of approximately 4:46 p.m. ET, according to data collected by the website PowerOutage.us.

The states with the most outages were:

• Pennsylvania: 258,919
• Ohio: 248,079
• Tennessee: 105,417
• West Virginia: 64,343
• Kentucky: 55,209

ABC News' Daniel Amarante and Sam Wnek contributed to this report.