Cars are deadly shelters during tornadoes

Fire Chief Jeff Reeves said they were not trying to outrun the twister.

"I think they were actually trying to get to a family member's house on the south side of town to help them and they just didn't make it over," Reeves said.

Val Castor, one of the many spotters who bring dramatic video of tornadoes to local TV stations in Oklahoma, said the number of people on the road during tornadoes seems to have increased every year since 1996, when the movie "Twister," which depicts meteorologists chasing tornadoes, came out.

He said driving during severe weather is extremely dangerous for the inexperienced because they don't know where a tornado will form or what direction it will go. Heavy traffic or a broken-down vehicle can stop people from getting away from the funnel cloud.

"The best advice is to make sure the tornado is completely gone before you venture out," he said.

After the tragedy, Missouri Gov. Matt Blunt warned people to say out of vehicles when a tornado is nearby.

Lie flat in a ditch or low spot
Weather experts say motorists and their passengers should find a sturdy shelter or lie flat in a ditch or other low spot, covering their heads with arms, coats or blankets if the tornado is moving in their direction. Overpasses and bridges should also be avoided — the overpass can create a wind-tunnel effect, and bridges can collapse.

The death toll from tornadoes this year is the highest since 130 people were killed in 1998, according to the weather service. The highest number of tornado-related deaths came in 1953, when 519 people died.

To date this year, 858 tornadoes have been reported in the U.S., although that number probably includes numerous duplicate sightings of the same twister.

Harold Brooks of the National Severe Storms Laboratory said the highest number of tornadoes ever recorded through May 11 of any year was in 1999, when 676 tornadoes were counted. Brooks said he expects the number of confirmed tornadoes through mid-May of this year to end up in the 650-to-700 range.

Altogether, 15 people died in Missouri from the same storm that devastated Picher, where six were killed. Two more people were killed in Georgia, where forecasters said at least six tornadoes touched down. One of those twisters struck McIntosh County's emergency management center, destroying the fire trucks and ambulances inside. Another man was killed in Alabama when his truck was hit by a tree limb as he was surveying storm damage.

The Environmental Protection Agency said it would check for high lead levels in Picher after the tornado blew through the heavily polluted former mining town where lead-filled waste is piled into giant mounds.

Miles Tolbert, Oklahoma secretary of the environment, said he did not believe there was any immediate hazard to the 800 residents. But he said more testing was needed.

More from msnbc.com In slump-hit areas, suicide rates on the rise Brokaw:  The night the wall came down Cosmic Log: How the Maya lived Is the swine flu shot as safe as regular vaccine? Scoop: Letterman extortion case heads to court Signs of the sacrifices of military life On Twitter: Breaking news updates | Weird and wild

MORE FROM WEATHER

Weather Section Front

Rains hitting Gulf Coast ahead of Ida Salvadoran town hit by landslide buries dead   Tornado rakes Oregon coastal town 200,000 see homes flooded in Mexico   Watch 3-day national forecast Drought worsens water woes in Venezuela   Stormy messes in Australia, Canada Weather Section Front   Add Weather headlines to your news reader: