(Bloomberg) -- Another wave of tornado-spawning thunderstorms is setto rip across the Great Plains and South this week, putting theU.S. within reach of a record year for life-threateningtwisters.

Severe storms will drench a swath of the country from Texas toMississippi over the next five days, according tothe U.S. Storm PredictionCenter.

Through Thursday, 369 tornadoes have been reported across thecountry, the most in five years and more than double the normalnumber of sightings.

$400 million in damage a year in U.S

An active jet stream and unusually balmy weather are to blame forthe burst of deadly tornado activity, the storm prediction centersaid. Strong winds have dragged storms into the warm, humid airthat’s blanketed the eastern half of the nation, creatingconditions ripe for a weather phenomenon that leads to at least$400 million in damage a year in the U.S.

“We have a severe threat starting today and continuing for eachof the next five days through at least Monday,” said Patrick Marsh,warning coordination meteorologist at the storm prediction centerin Norman, Oklahoma. “Through mid-March, we are on a record ornear-record pace.”

The atmospheric moisture across the southern U.S. in January wasmore typical of April, Marsh said. A confirmed tornado touched downin central Massachusetts in February, a first, while there wasstill snow on the ground.

The peak of tornado season varies across the country. Activityis concentrated in the Southeast early in the year, drifting intothe Great Plains’ “Tornado Alley” in May and June before headinginto the Northeast by early summer.

U.S. averages 1,200 tornadoes a year

The U.S. has more tornadoes than any other country, according to areport by Lloyd’s of London. The nationaverages about 1,200 tornadoes a year, with the storms killing asmany as 60 people and injuring 1,500, Lloyd’s said.

Tornado “outbreaks,” or storm systems that spin out multiplefunnels in a limited time and area, are becoming more frequent inthe U.S., according to study published in the journal Science inDecember. Still, the trend isn’t consistent from what some modelspredicted would result from global warming, the study found.

Related: 6 ways to tornado-proof your home

This could mean climate change isn’t having an impact on tornadonumbers, or it may be because scientists just haven’t figured outwhat effect it’s having, lead author Michael Tippett, a seniorresearch scientist at Columbia University’sInternational Research Institute for Climate and Society inPalisades, New York, said in the report.

Rising costs

One thing’s for certain: Costs associated with tornado damages arerising as the number of people living in the path oftwister-producing storms rises.

“Since 1980, losses due to severe thunderstorm events in theU.S., which includes tornadoes, hail and straight-line winds, haveincreased dramatically largely due to socioeconomic effects,” MarkBove, a senior research meteorologist for Munich Reinsurance America Inc., said in anemail.

The system pushing into the central U.S. may create more severeweather as it pushes east, said Bob Oravec, senior branchforecaster with the WeatherPrediction Center in College Park, Maryland.

“It definitely is going to have the potential for a multi-dayevent,” Oravec said.

And it could just be the first of several such systems, he said.Long-range models show the potential for a train of storms throughthe central U.S. for the next few weeks.

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