Tornadoes aren't close to being the region's biggest weather worry.

Twisters have formed in the Philadelphia area, but generally they're short-lived and non-lethal.

History suggests the region is highly unlikely to be struck by a tornado as devastating as the one that killed two dozen people in Oklahoma Monday while leveling blocks of homes.

Perhaps the Philadelphia area's worst tornado tragedy happened on July 27, 1994, when three people were killed in Limerick, Montgomery County.

On Oct. 27, 2003, a 77-year-old woman was struck and killed in Hainesport, Burlington County, by a nine-inch thick tree limb that was tossed about 100 feet, according to the National Weather Service. That tornado lasted only about 15 minutes, traveled only a half-mile, and was rated as an F0, the weakest kind of tornado, with winds of 65 to 85 m.p.h.

Only one other tornado-related death was reported in Pennsylvania, New Jersey or Delaware this century. On Nov. 10, 2002, an 81-year-old man was killed in his home when a tornado hit Clark, Pa., north of Pittsburgh. That twister, an F2 (winds up to 135 m.p.h.), traveled seven miles, destroying 15 homes and doing major damage to another 13, according to the weather service.

Anything stronger than an F0 or F1 is rare in the Philadelphia area, according to meteorologist Joe Miketta of the weather service's Mount Holly office.

The lethal Limerick tornado was an F3 (winds up to 165 m.p.h.), still less powerful that the F5 twister that hit Oklahoma with winds of over 200 m.p.h.

So what is the region's deadliest kind of weather?

That would be heat, Miketta said.

Some 215 people in Philadelphia have perished due to heat since 2000, including 29 just in July 2011, according to the federal Storm Events Database.

The total accounted for 84 percent of the 255 heat-related deaths statewide, a stat so lopsided it raises questions about variations in medical standards.

"The Philadelphia medical examiner's office uses a broader definition than many other cities when it comes to determining heat-related deaths, including factors like room temperature and pre-existing medical conditions," the Associated Press explained in a story about the deadly heat wave of July 2011.

"I've been told the city of Philadelphia does it the right way," said weather service meteorologist Anthony Gigi.

But heat is still the No. 1 killer nationwide, averaging 117 deaths a year over the decade from 2003 to 2013, according to the National Weather Service.

Next nationally are hurricanes and tornadoes, 109 each, followed by 89 for flooding, 51 for wind and 46 for rip currents.

Yes, rip currents, even though they happen only along coastlines, kill more people annually than lightning (35), cold (27) or winter storms (24).

In Pennsylvania, 18 people died from cold or windchill since 2000, while 42 died because of flooding, including flash floods.

In New Jersey, rip currents accounted for 26 deaths since January 2000, more than from lightning (16) or flooding, including coastal flooding (10).

As for heat-related deaths in Jersey, the numbers seem questionable. The federal database shows only 11 since 2000, and yet the state health department, in presenting a report in 2008, stated, "Typically, in New Jersey, fewer than ten people die annually due to excessive heat. However, 30 people died in 1999 and 18 died in 2002, two of the hottest summers on record."

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com.