USA has the world's most extreme weather

Doyle Rice | USA TODAY

North America — and the USA in particular — has the world's wildest weather extremes: No other part of the planet can boast its ferocious weather stew of hurricanes, tornadoes, droughts, floods, wildfires, blizzards, heat waves and cold snaps.

"You'd be hard-pressed to find another patch of land on Earth the size of the USA that boasts such a variety of such intensely extreme weather inside its borders," says meteorologist and author Robert Henson of Boulder, Colo.

"We get more high-impact weather than any other country on the planet," agrees Sean Potter, a meteorologist and weather historian in New York City.

This wild, varied and extreme weather provides a dramatic backdrop for a new, seven-part Discovery Channel series, North America, which premieres Sunday at 9 p.m. ET/PT. According to Discovery, the series "will reveal the intimate stories of animals struggling to survive in unforgiving weather and rugged terrain."

Filmmakers say that weather plays a huge part in the series. "North America has some of the most extreme weather on the planet — something I'm sure will resonate with a lot of Americans," says series producer Huw Cordey of Discovery.

Our wild weather has always fascinated us, and was a shock to the early pioneers. "Europeans who settled America from east to west were progressively amazed by the spectrum of conditions they encountered," wrote Henson in his book The Rough Guide to Weather.

What makes it so wild?

"The U.S. is uniquely situated in the mid-latitudes — about halfway between the equator and the North Pole — and between two oceans," Potter notes. "The contrast of cold, dry, Arctic air from Canada and warm, moist, tropical air from the Gulf of Mexico, Pacific and Atlantic help fuel the massive storms that move across the country year-round, bringing everything from blizzards to heavy rain and thunderstorms, depending on the time of year," he says.

Tornadoes, such as the ones that slammed Texas on Wednesday, are nearly a uniquely American phenomenon. Each year, "the U.S. experiences about 80% to 90% of all of the tornadoes that occur across the world," says Randy Cerveny, a professor of geography at Arizona State University.

"The U.S. averages more than 10,000 severe thunderstorm events per year, with more than 1,000 tornadoes," Potter says. "By comparison, China, which is slightly larger in size, sees around the same number of severe thunderstorms, but fewer than 10 tornadoes per year."

Also, as for wild temperature extremes, the fact that North America has no east-west mountain range means there's nothing to stop the cold winds from the north meeting the warm weather from the south, says Discovery's Cordey.

"The mountains allow the influx of very cold air from Canada and even Siberia to spill down into the center of the country and for massive humidity and hurricanes to come up from the south, such as the Gulf of Mexico," Cerveny says.

These weather phenomena shape the landscapes, which in turn shape the wildlife, as the Discovery series will showcase. "The deserts depend on the annual monsoons — pretty much the only proper rain for the year — and the animals have to adapt accordingly," Cordey says. "The Plains are racked by extreme weather changes — very cold winters, where the ground can be thick with snow, to blistering hot summers."

Many animals can't cope with these massive seasonal shifts and migrate (or hibernate) in the winter, he says. "Indeed, North America has some of the greatest migration spectacles on the planet. No coincidence, as this is a direct result of the weather changes."

Cerveny agrees: "Without question, wildlife adapts to climate so we find very diverse and — because of the incredible extremes in climate — adaptable wildlife in this country.

"From the bison of the Great Plains (adjusting to the low rainfall and grasslands) to the crocodiles of the Florida Everglades (adapting to the wet and marshy conditions of Florida) and the beavers of northern states (acclimating to the colder, and more damp, conditions of the northern states), the wildlife of the U.S. has clearly adapted to the specific conditions found across the country," he continues.

"In some cases, the incredible diversity of climate, even within short geographic distances, has led to actual differentiation of species. In the Grand Canyon, for instance, there are two distinct species of squirrels — one on the north side of the canyon and another on the south side," Cerveny concludes.

"An extravagant array of wildlife learned how to adapt to the weather between Atlantic and Pacific long before this land became the USA," Henson says. "If a species is well-suited to the mountains, Plains or coastline, it can survive even if some members are lost to a harsh winter or a brutal storm."

"What remains to be seen," Henson says, "is how the USA's wildlife will adapt not to a single weather event but to a sustained change in climate, as our warming trend continues and both drought and heavy rains become more intense."