When I was young, 100 degree F. days were rare at the weather station adjacent to the Forest Service office in Mount Shasta City. There were two such days in the five years I lived at Mount Shasta in the 1980s. One was in 1987, when data was not recorded at the FS weather station, but 102 was reached at Frank Christina’s home near the high school.
Things have changed. Six 100 degree days were recorded in 2021 and five this year so far. Is this an aberration or a trend? To try and answer this, I looked at records for the FS weather station going back to 1948, as available from the NOAA Medford Climate website.
The first 100 degree day in this period occurred in September 1950. In the 30 year period from 1950 to 1979, there were eleven 100 degree days, or about one every three years (0.37/year). For the next 30 year period 1980 to 2009, there were also eleven 100 degree days, four of which were recorded during an extreme heat wave in August 1981.
For the remaining full year period, 12 years from 2010 to 2021, there were seventeen 100 degree days or about three every two years (1.42/year). This is a 420% increase in 100 degree days compared with the previous 60 years.
The eleven 100 degree days experienced in the 14 month period June 2021 through July 2022 is equal to the number in 30 years during the 1950 to 2009 era.
So, what do you think, aberration or trend?