This morning, the temperature at the summit of Mount Washington, NH, briefly dipped below freezing, resulting in the first ice since early June and the first snowflakes of the season.
“This morning, the summit is seeing temperatures dip below freezing for the first time since early June and we have also observed the first glaze ice & snowflakes of the 2023/24 season. The ice/snow will be limited to above 6000 feet and is expected to melt quickly. However, Thursday will remain cold and windy on the higher terrain, so pack/dress like you would for an autumn hike.”
While accumulations were light and brief, it is a reminder that winter weather can occur during any season on the summit and is a sign that more cold and ice is right around the corner.
Mount Washington has the second-fastest wind speed ever recorded on Earth and the fastest wind speed ever recorded by a human at 231 mph (372 kph). Many people may wonder how its weather could rival Antarctica, Mount Everest, or the Sahara Desert. It may seem odd that there could be a place that is so harsh in the heart of New England, but there are several factors that make for a perfect storm.
Mount Washington’s Averages and Extremes
- Fastest Wind Speed: 231 mph (372 kph)
- Avg. Annual Temperature: 27.3˚F (-2.6˚C)
- Record High Temperature: 72˚F (22.2˚C)
- Record Low Temperature: -47˚F (-43.9˚C)
- Average Precipitation: 96.87 in (246.05 cm)
- Record Precipitation: 130.14 in (330.6 cm)
- Average Snowfall: 281.2 in (514.25 cm)
- Record Snowfall: 566.4 in (1,438.66 cm)
Why is the weather there so extreme? North America has three major wind patterns that flow west to east. These three patterns all happen to converge over the White Mountains. Also, wind travels unimpeded for more than one thousand miles before it reaches the peak of Mount Washington at 6,288 ft (1,916.6 m). This extremely long fetch means that high winds are quite typical as the mountain is significantly taller than any surrounding peaks.
The second factor for wind also has to do with how tall the mountain is compared to its surroundings. The Presidential Range, of which Mount Washington is the highest peak, runs north/south. With Washington in the center of the range, all of the weather gets funneled up and over the summit. As the air flows over the summit, it gets pinched between the peak and the tropopause, which is the troposphere’s upper boundary. This is known as the Venturi effect. The simplest way of visualizing this effect is to think of it as putting your finger over the end of a garden hose and having the water speed up as it exits the hose.
Living at the summit, observers from the Mount Washington Observatory keep track of the extreme environment. They take hourly weather readings 24 hours a day, 365 days a year. With hourly data starting in 1932, the Observatory has some of the best weather records in the world. This data is crucial in understanding our changing climate and what we can expect in the future.