The worst weather in the world

“Hurricane-force winds rage about a third of the year, cold is rare outside the Arctic, and there’s a lot of rain,” says science communicator Maiya May of Mount Washington, which is considered to have some of the worst weather on earth.

The summit of this relatively small mountain held the record for the fastest wind speed on the planet for more than 60 years, when experts measured a gust of 372 km/h in April 1934. Even in summer, when the winds are calmest, they average around 40 km/h.

"We basically get 100 mph winds once a week during the winter. Usually a 100 mph gust is enough to knock me over, and I've seen winds up to 140 mph," said Tom Padham, a Mount Washington weather observer.

Mount Washington is also very wet, with an average of more than 90 inches (2,286 mm) of precipitation per year and more than 300 inches (7,163 mm) of snow, ice, and hail. It is foggy about two-thirds of the time. The summit is also susceptible to direct lightning strikes.

Temperatures on the mountain aren't exactly comfortable, either. Monthly averages range from -14.4 degrees Celsius (-50.4 Fahrenheit) in January to 10 degrees Celsius (-50.4 Fahrenheit) in July. "Any exposed skin, even a millimeter, feels like a bee sting or a mild sunburn, so it's definitely not comfortable here," weather observer Francis Tarasiewicz said in February. Earlier that month, thanks to a combination of 110 mph winds and an arctic chill, the Mount Washington Observatory set a new record for the coldest wind gust ever recorded in the United States, hitting -78 degrees Celsius (-78.4 Fahrenheit), with an actual temperature of -43 degrees Celsius (-43.4 Fahrenheit).

Francis Tarasiewicz, an engineer at the Mount Washington Observatory, humorously notes that much of the mountain's weather problems are down to "luck." The mountain's unique conditions come from a combination of factors, including altitude, geographic location, and latitude on Earth, all of which contribute to making the weather as bad as possible.

Mount Washington, for example, is located almost halfway between the North Pole and the equator—right in the path of the polar jet stream. This band of wind gets its energy from the collision of cold air from the north and warm air from the south. “In the mid-latitudes, we have a lot of storms. But what makes it different is that we have a very humid atmosphere. Humidity leads to things like instability,” says Tarasiewicz.

The mountain's isolation from surrounding terrain makes matters worse. "It's the tallest mountain in about 1,000 miles, so there's not much terrain to slow the jet as it crosses the U.S. and into New England," Tarasiewicz added.

The frigid winds are further enhanced by the Venturi effect, which not only places Mount Washington in the path of the jet stream, but also sits in a giant natural funnel that compresses and accelerates the air flow over and around the summit.