Falling at the end of hurricane season and prior to major winter storms, November has historically eluded billion dollar weather disasters in the U.S.  But economic damages from Sunday’s tornado outbreak could exceed $1 billion says a leading risk modeling firm, making it the most expensive weather disaster to occur in November in 25 years of records.

“Given evidence we’ve seen, it’s likely it will exceed $1 billion,” says Matt Nielsen, a meteorologist at RMS, a firm that projects and assesses disaster losses. “If we compare it to some of the other analog [similar] events for this year, the billion dollar number seems to be consistent.”

* In Washington, Ill., alone, about 1,000 homes were damaged or destroyed.

Tornado damaged homes are seen on November 18, 2013 in Washington, Illinois. (Photo by Tasos Katopodis/Getty Images)

* Illinois governor Pat Quinn declared 13 counties disaster areas in the state.

* In Indiana, 12 counties have reported widespread storm damage.

* Destructive thunderstorms and tornadoes also occurred in Kentucky and Missouri.

“The thing that set [the outbreak] apart is that it occurred farther north [than usual],” Nielsen says. “Usually at this time of year we see outbreaks further south, where there is a much lower population density.”

Two destructive EF-4 tornadoes (on the 0-5 scale) occurred in Illinois, for the first time on record in November.

“The two EF-4 tornadoes that struck Illinois were the 2nd and 4th most northerly EF-4s ever recorded in the U.S. during the month of November,” writes wunderground meteorologist Jeff Masters.

Sunday’s outbreak, should its price tag pass the billion dollar mark, would be the 8th weather disaster crossing that threshold in 2013.

Severe weather outbreaks make up of five of the other 7 billion dollar weather disasters, says Aon Benfield, a reinsurer.

U.S. billion dollar weather disasters in 2013, not including the November 17 severe weather outbreak (Weather Underground/Aon Benfield)

2013’s steep economic toll from severe weather might come as a surprise given an unusually low number of tornadoes compared to average. Prior to Sunday, only 818 tornadoes had been confirmed this year, the lowest year-to-date count since 1988.

But there have been 9 destructive EF4 and EF5 tornadoes, slightly above the 30-year average of 7.7.

Thus twisters have been few, but violent – while happening at unusual times.

The most prolific tornado days have occurred in November (81 tornadoes– preliminary count), January (62), and October (42) – outside the usual spring-summer peak noted RMS’ Nielsen.

“Sunday’s big tornado outbreak is yet another atypical storm of what has been an unusual 2013 severe weather season,” Nielsen says.