Temperature related variables

Early and late season frosts

 
 

Figure 26 - Date of a) the first ground frost in days after the 1 August, 1960 to 2005 and b) the last ground frost before the end of July, in days from the 1 August, 1961 to 2005, at four Scottish stations, with smoothed curves showing a running average.

Table 14 - Changes in the dates of the first and last ground frost (in days) starting from 1 August, and changes (in days) in the length of the frost-free season, for four Scottish stations for 1961 to 2005. Values in bold show that we are 95% confident (statistically) that the change is part of a measurable trend.

 

Threave Blythe Bridge Kinloss Wick
First ground frost 3.4 10.2 7.3 11.8
Last ground frost -22.5 -15.0 -12.1 -24.0
Frost-free season 29.1 24.5 20.0 38.8

 

Regional trends

 

  • The length of the frost-free season has extended, by between 20 and 40 days.
  • At each of the stations, the first frost is happening later but we can see no clear trend. However, there is a trend towards an earlier last frost by between 12 and 24 days since 1961.
  • There are still big differences each year in the dates of the first and last frost and summer frosts are still common at each of the four sites.

Future trends

 

  • The UKCIP02 scenarios report does not give any estimates for changes in frost dates. But the expected increases in minimum temperatures should also mean a reduction in the number of frosts.
  • The expected change in length of the growing season also suggests that there may be a longer frost-free period.