September 2024 saw the unprecedented weather event that was Tropical Storm Helene hit Western North Carolina with high winds and significant rainfall. While it had a devastating impact on the area, the Grandfather Mountain nature park was extremely fortunate to receive only minor damage.
That said, the park’s official weather reporting stations did have equipment go out during the storm, which resulted in a few days of missing wind and temperature data. Staff members were also not able to access the sites to record precipitation measurements in the immediate aftermath of the storm.
Nonetheless, the data that was available and collected reflects some of the extreme conditions that the mountain experienced during Helene, including the second-highest monthly rain total on record for September.
The average high temperature for September 2024, not including three days of missing data, was 60.80 degrees Fahrenheit, with an average low of 51.89 degrees and a mean of 56.35 degrees.
The warmest temperature recorded for the month was 70.7 degrees on Sept. 22, more than 8 degrees shy of the mountain’s record September high of 79 degrees, observed Sept. 24, 2010. Generally, September sees fall weather conditions take hold on Grandfather Mountain, with cooler temperatures arriving.
Sept. 4 saw the coldest temperature recorded during the month with 43 degrees. The lowest temperature ever observed on Grandfather Mountain in the month of September (not counting wind chill) was 24 degrees on Sept. 30, 1967.
The weather station on the Mile High Swinging Bridge registered a wind gust of 72.6 mph on Sept. 27, the day Helene struck, before the equipment went down for the remainder of that day and month.
The weather station near the Swinging Bridge reported 21.13 inches of precipitation for September, not including three days of missing data at the end of the month. Precipitation at the top of the mountain includes rain and the liquid equivalent of any frozen precipitation (when applicable).
Observations recorded near the park’s Wilson Center for Nature Discovery totaled 24.85 inches of precipitation for the month, not including the three days of missing data. Additionally, the rain gauge at this site was overflowing at the time of measurement, from the storm. Precipitation is also measured at the latter location, as high winds can make it difficult to record accurate observations at the top.
The mountain’s rainiest September was recorded in 2004, when 32.30 inches were observed near the bridge. That year saw widespread flooding across the region from Hurricanes Frances, Ivan and Jeanne. The driest September on record was observed in 2019, when 0.68 inches were recorded.
Not including the missing data, there were 23 days of at least trace amounts of recorded liquid precipitation (rain and the liquid equivalent of frozen precipitation, when applicable) for September 2024, matching the record high seen in 2020. The day with the highest amount of this precipitation observed was Sept. 27, when 10.10 inches were recorded at the top. The day with the highest amount of precipitation observed on record for September was Sept. 8, 2004, when the weather station observed 11.30 inches.
Weather Reporting
The Grandfather Mountain Stewardship Foundation records and reports data in two different ways:
- The park maintains an automated weather station at the top of the Mile High Swinging Bridge. The N.C. State Climate Office assists the foundation in calibrating the machines and ensuring overall accuracy of data.
- Grandfather Mountain has been an active member of the National Oceanic and Atmospheric Administration’s (NOAA) Cooperative Observer Program since 1955 by reporting weather data from locations near the Mile High Swinging Bridge and the Nature Museum (now the Wilson Center for Nature Discovery).
For more information on weather at Grandfather Mountain, visit www.grandfather.com/weather.