Northern California is looking a lot like Tornado Alley these days.
Just north of Sacramento, two reported weak tornadoes struck this week in Colusa County, which did not have a single tornado report from 1950 to 2010, according to the Weather Channel. Colusa has now had three reported tornadoes this year and four in the past five months. That's some serious action for a state that averages about five tornadoes per year. [Infographic: Tornado! An Inside Look at Tornado Season]
No witnesses saw the touchdown of yesterday's (March 23) reported EF-0 tornado — the weakest ranking with winds between 65 and 85 mph (105 and 137 kph) — but people did see a funnel cloud and six homes reported damage, the Sacramento Bee reported. Another funnel cloud was captured on YouTube on Monday (March 21).
The severe storms in Colusa County were caused by an upper level low-pressure system swinging through behind a cold frontal system, said Johnnie Powell, a meteorologist with the National Weather Service in Sacramento. Southerly winds blowing off the coast mixed things up in the atmosphere, and when the sun came out, it added fuel to the storm.
"That's the way it sort of works in the Midwest, but a lot more extreme," Powell told OurAmazingPlanet.
But Colusa County is not in Tornado Alley, where warm, moist Gulf of Mexico air collides with cool, northern air, creating the massive storms that spin off tornadoes.
Colusa's wild weather has been driven by a blocking pattern in the north Pacific Ocean, which is forcing the jet stream south, with Colusa in the crosshairs. "As long as that pattern stays that way, they'll just keep coming on in," Powell said.
Outside the zone
As Colusa County is showing, every state — even Alaska — can have tornadoes. Maine has about two tornadoes each year, and Arizona has three. For the first time, Minnesota led the United States with 113 tornadoes last year.
New Jersey and New Hampshire had one tornado each, last place among states that saw tornadoes in 2010. California had eight tornadoes in 2010.
Of course, tornadoes aren't a purely American weather menace. Touchdowns have been reported on every continent except Antarctica.
Tornadoes don't just form during the day either. Night twisters can be some of the most deadly, because tornadoes are hard to see at night and people tend to sleep through warning sirens. Thirty-nine percent of tornado fatalities and 42 percent of killer tornado events occur at night. (A killer tornado event is considered one where at least one death is linked to the tornado.)
Tornadoes can also strike during any time of the year (November is often called the second tornado season), even during the winter. A tornado hit New York City at night in September last year.
In 2010, 45 people were killed by tornadoes across the United States.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.