Longer Days Ahead

2016-03-19 20:48:44.000 – Michael Dorfman, Weather Observer/IT Specialist


With the first day of spring coming up (tomorrow!), I decided to get a bit excited about the warm temperatures we’ll see on the summit mid-summer. While it may not seem that warm to valley-dwellers, our record warm temperature recorded on the summit is a balmy 72F degrees (which was recorded twice in our history).

In celebration of the coming warmth, I’ve put together some numbers from the summit. The graph below shows average temperature and relative humidity compared to wind direction from our digital sensors since 2005. While this doesn’t hold true for every situation, you can generally predict what type of air mass you’ll see based on the direction it comes from. When we see prevailing winds from the north, we’re likely to see cold (from higher-latitude Canada) and dry (from above a continent) air mass. Temperatures and relative humidity soar when we have a flow from the east through southwest, as we see air from more southern latitudes and air that originates over the ocean.


I also decided to dig up some of our 30-year average monthly temperature stats and have compared them with the length of day in the diagram below. As you can easily see, our temperature and length of day do not directly correspond to each other; our longest day in June occurs a month before our warmest temperatures in July.


The National Weather Service explains this phenomena with relative clarity:

There is a lag between the longest day of the year and the warmest average temperatures for most mid and high latitude locations. 

In northern OH/northwest PA, the maximum daily temperature occurs nearly 3 weeks later in mid July. Just as the warmest part of the day usually occurs several hours after noon, when the sun is highest in the sky, so too does the warmest part of the summer lags the summer solstice. This lag is due to the time required for ground and water to heat up. Average temperatures continue to climb until the sun drops lower in the sky. While the effect is evident in a daily temperature plot, it is more readily apparent by looking at changes in the monthly average temperature. In Cleveland, July averages 3.3°F degrees higher than June, with August also warmer than June by 2.8°F, even though the length of days in August is considerably less than the length of days in June.(source: http://www.weather.gov/cle/Seasons)
So if you’re planning on heading above tree line, even though the days may be sunny and long, winter won’t loosen its grip on the summit until later in the summer.  Despite the warmer temperatures, it should be noted that we’ve observed snow events every month of the year.  Additionally, our daily record lows only include a small handful of above-freezing temperatures.  Be sure to visit our website and read our forecast to get a better idea of what you’re hiking into! 


Michael Dorfman, Weather Observer/IT Specialist

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