Mount Washington-Home of the Country’s Least Sunshine?

2017-03-06 10:31:30.000 – Nathan Flinchbaugh, Summit Intern

 

If you’re lucky enough, you’ve had the opportunity to stand on the summit and experience the amazing view that stretches 130 miles, offering views of the Atlantic and nearby Canada. And if you’re at all familiar with the weather on Mount Washington, you know that you’re lucky, as these days are few and far between. The summit spends a good portion of the year in the clouds, which can quickly suffocate your view from 130 miles, to barely able to see your own feet in a short period of time. With these inherent conditions, you’re not likely to see much in the way of sunshine at the summit either, which begs the question…Is Mount Washington the home of the country’s least sunshine?

In short, the answer is no…but almost. One less known part of our hourly weather observations is the variable “sunshine minutes.” Each hour, along with other vital information we collect, such as temperature and wind speed, the number of minutes we see the sun each day is also carefully recorded. And just like temperature and wind, this information gets sent hourly to the National Weather Service, and eventually to the National Climatic Data Center (or NCDC for short). The NCDC takes our carefully recorded “sunshine minutes” and converts them to a variable called “percent of possible sunshine.” This measurement is the percentage of time that sunshine reached the earth when it was possible (sunrise to sunset).

The 5 least sunny locations in the United States, courtesy of NCDC.

NCDC’s results from this calculation indicate that Mount Washington is actually tied for 2^nd with Quillayute, WA for the least amount of sunshine in the nation. During the time the sun is up, it is only strong enough to cast a shadow a whopping 33% of the time. Juneau, Alaska takes home the gold medal with merely 30% of possible sunshine. Coming in at the opposite end of the list is Yuma, Arizona, with 90%, making it the sunniest location in the United States.

The top 5 sunniest locations in the United States, courtesy of NCDC.

For comparison, below is a graph showing percent of possible sunshine by month for the summit, as well as a few other New England locations.

Percent of possible sunshine by month for Mount Washington, and four other New England locations.

At least when it comes to these locations, Boston takes the cake as New England’s sunniest, coming in at an annual average of 58%. Mount Washington obviously lags very far behind, receiving really only half of the sun Boston sees. While areas below tree line receive the most sun during the summer, the peak of Mount Washington actually sees its highest percentage of sun during the shoulder seasons. This is mainly due in part to convective clouds that pass over the summit during the summer, some of which contain thunderstorms; these are not as frequent in the spring or fall. All locations see a drop off in sun during the late fall and early winter, however the drop is much sharper away from the coast.

As we head deeper into meteorological spring, the days will become longer, and hopefully we’ll start to record some more of those sunshine minutes along with the rest of New England. Until then, if you ever find yourself yearning for more sunlight, know that it’s coming, and it could always be worse. Unless you happen to be reading this from Juneau, Alaska!

 

Nathan Flinchbaugh, Summit Intern