America suffered its most active week of tornadoes on record, meteorologists said as they sized up a wave of storms that left 44 people dead from Kansas to Georgia.
The deadly tornadoes began early in the week in Missouri, Kansas and Tennessee, followed by two rounds of twisters in the Oklahoma City area on Thursday and Friday. Storms combined with straight-line wind, lightning and floods as they reduced hundreds of homes and businesses to splinters and piles of loose bricks.
"We just don't have a down day; that's what's been very unusual," Rich Thompson, lead forecaster at the Storm Prediction Center of the National Weather Service, in Norman, Oklahoma, said.
"It just doesn't seem to stop," he said.
Storms pelted several states on Saturday, although they weren't as severe as some of the earlier turbulent weather.
A system in Missouri spawned tornadoes that damaged outbuildings, overturned cars and downed power lines.
At least one tornado touched down in Indiana. Torrential downpours flooded streets and fields and forced the postponement of Saturday's qualification for the Indianapolis 500 car race.
In Kentucky, 10 people were injured after a storm swept through the northeastern part of the state. The National Weather Service confirmed a tornado in the area.
Tornadoes also hit six central Illinois counties on Saturday, damaging homes and pelting trees, officials said. No major injuries were reported.
While tornadoes are common in May, the number reported in the first part of this month has been extraordinary, said Dan McCarthy, warning coordination meteorologist at the Storm Prediction Center.
By Saturday, about 300 tornadoes had been reported since the start of the month, about 100 more than the most recent comparable rash, in 1999. Until now, that 1999 barrage had been the record for any 10-day period since record-keeping started in the 1950s, McCarthy said.
About 70 percent of all tornadoes are reported in April, May and June.
"What is happening this week is that we have a persistent warm air mass in place and a persistent jet stream extending from the Southwestern US into the central Plains," McCarthy said.
Those conditions were ripe for producing thunderstorms, which can rotate and form tornadoes.
Changing weather conditions were expected to reduce the risk beginning yesterday.
More than 100 people were injured in the Oklahoma City area by two tornadoes that struck on Thursday and Friday night. But only a few were hospitalized Saturday, and only one remained in critical condition.
President George W. Bush issued a disaster declaration on Saturday for Oklahoma, clearing the way for federal aid. Earlier in the week, he did the same for tornado-battered parts of Tennessee, Kansas and Missouri.
More than 300 homes and 35 businesses were destroyed in Oklahoma alone and the state insurance commissioner's office gave a preliminary damage estimate of US$100 million.