The top graph shows the 30-year average last date of frost at Stornoway, Durham, Oxford, Armagh and Braemar (the value for each year is the 30-year average ending on that year so the value for 1910 spans 1880-1910.)
The bottom graph is the same format but shows the 30-year average first frost of autumn.
The dates are calculated as Julian Day so 1st April is 91, 1st May 121 etc (disregarding leap years)
The most dramatic changes seem to be at Stornoway where the average date of the first frost is now at the end of November, compared to end of October/early November 50 years ago.
UK frosts
Originally Posted by: Viking3