Due to winter weather, staff members at Grandfather Mountain were only able to record weather 21 of the 31 days in December at the official U.S. Weather Service reporting station next to the Mile High Swinging Bridge.
This was the fourth coldest December on record at Grandfather Mountain. The average high temperature for December of 31.62 degrees was 6.97 degrees colder than normal. The average low temperature was 14.43 degrees, 9.52 degrees colder than the 55-year average for the month. The coldest temperature of the month was minus four degrees on December 15, breaking the record for that date of minus three degrees set in 1963. A daily low temperature record was tied on December 8 when the temperature dipped to minus one degree, tying a mark set in 2006.
During the 21 December days that weather was recorded, no snow was measured at the US Weather Service reporting station - because by the time employees were able to get to the top of Mountain the accumulation had blown away. The "unofficial" snow total for December 2010 calculated from the melted snow liquid level at the Top Shop is 58.2 inches of snow. The "unofficial" snow total measured by employees at the Entrance Gate was 63.03 inches. Grandfather has only officially recorded 0.16 inches of snow this winter which is 11.76 inches below normal for this time of year.
Wind gusts over 60 mph were recorded nine times. The highest three-second gust recorded for the month was 89 mph December 14. The December rainfall total of 2.93 inches was 1.16 inches, or 28 percent, below normal. The rainfall total for the year was 59.05 inches. The average annual rainfall at the Mountain is 62.98 inches, making the 2010 total 3.93 inches, or six percent, above normal.
In 2010, the month with the most rain was January with 10.12 inches and the month with the least rain was October with 1.49 inches. January’s rainfall total made it the third wettest January ever at Grandfather. The most rain to fall in one day during 2010 was 4.06 inches on March 22. The rainiest day ever at Grandfather Mountain was September 8, 2004 when 11.3 inches of rain fell.
Temperatures were warmer than usual at Grandfather Mountain in 2010. The average mean temperature was 48.98 degrees, which was 2.6 degrees warmer than normal. The average high temperature for the year of 56.53 degrees was 2.99 degrees warmer than normal and the average low temperature of 41.43 was 2.2 degrees warmer than normal.
Twenty-seven new daily high temperature records and two new daily low temperature records were established in 2010. Eleven daily high records and one daily low record were tied.
The summer brought warm temperatures that made for the warmest June, July and September ever at Grandfather Mountain. The second warmest August was recorded.
A reading of 80 degrees on April 7 broke the record for the highest temperature ever recorded during the month of April. The previous record was 76 degrees set April 25, 2009 and tied April 26, 2009. A similar record was broken in September when the temperature reached 79 degrees on September 24. The previous warmest temperature ever recorded during the month of September was 78 degrees on September 1, 1993.
The warmest temperature in 2010 was recorded July 9. A reading of 83 degrees tied the warmest temperature ever recorded on the Mountain set on August 22, 1983 and tied July 26, 2005.
The coldest temperature in 2010 was minus seven degrees on January 9. The coldest temperature ever recorded at Grandfather is minus 32 degrees on January 21, 1985.
In 2010 wind speeds exceeded 60 mph 51 times. The highest three-second gust recorded was 95.5 mph February 11. The highest gust ever recorded on Grandfather’s Swinging Bridge anemometer, which was installed February 2007, is 106.95 mph on February 11, 2008.
Total recorded snowfall for 2010 was 80.96 inches compared to a 55-year average of 53.70 inches, up 50 percent. Due to winter weather, Grandfather's weather was not recorded eight days in January, 11 days in February and 10 days in December making the actual snowfall total on the Mountain an estimated five to seven feet more than reported.
For more information on the 55 years of weather data from Grandfather Mountain, see the interactive weather database at www.grandfather.com.