The coldest winter in London for 8 years.
Just when we all thought we’d got away with another relatively mild winter and spring was on its way, the temperature in the garden plummeted to -4C as freezing cold air and snow direct from Siberia was blasted across the country by what the media dubbed “the Beast from the East”. It felt like the coldest winter UK temperatures for years, but was it?
Although most plants in the garden should, according to the books at least, survive down to -5C, this was certainly the coldest winter in the garden since most plants have been in the ground, and the first time they have been tested beyond a few days at -2C. Time will tell if there have been any casualties. Some plants, like the echiums below, look utterly miserable while others like the Citrus reticulata and Banksia integrifolia seem to shrug off the cold and snow without a worry.
The media claimed that this cold snap was “historic” and it seems that there were indeed record low temperatures and snowfall for the month of March. But overall, how cold was it, and how did the minimum temperatures compare with those of last winter, and of previous cold winters?
Minimum temperatures compared with previous years
To answer this question I analysed data from the Met Office MIDAS database, identifying the minimum temperature recorded by each station, checking and cleaning any erroneous records. The data were then plotted as isotherm maps using ArcGIS software.
The resulting maps (below) show that the minimum temperatures from February 28th to March 1st 2018 were surprisingly consistent across the country, with most areas recording lows of slightly above or below -5C. This is a relatively mild winter temperature for most parts of the country, but for London and the southwest which also experienced temperatures of around -5C this is relatively harsh, and many gardens in these areas saw the lowest temperatures since 2010 (when Kew Gardens went down to -10C and RHS Wisley gardens -12C).
Winter in 1991 saw unusually low temperatures in London and the southeast, with Kew Gardens dropping to -10.9C and even the usually mild St James’s Park in central London dropping to a record -8.3C.
Winter of 1987 was the stuff of nightmares for exotic gardening enthusiasts, as unusually low temperatures were experienced in the southwest, including the usually frost-free Tresco Abbey Gardens which were devastated by temperatures below -7C.
The winter we really don’t want repeated is that of 1982 which saw record lows in many parts of the country including -15.5C in Edinburgh Botanic Garden, -15.1C at RHS Wisley and -16.1C at Cambridge Botanic gardens. That year also recorded an all-time record low of an unbelievable -27.2C at Braemar in Scotland. Perhaps climate change means such winters are a thing of the past?
In the second part of this post I will look at whether minimum temperatures in the past can be used to guide what plants we can safely grow, and what it’s worth trying to grow, where we live. I’ll use the same data to explore the urban heat island effect which enables gardeners in city locations to grow more tender plants, and I will plot the most detailed and up to date hardiness maps for the country yet published.
Met Office (2012): Met Office Integrated Data Archive System (MIDAS) Land and Marine Surface Stations Data (1853-current). NCAS British Atmospheric Data Centre, 2018.