UKMO climate information for April give average temperatures for Kent at for coasts and more inland.
Current, April 2016, temperatures are several degrees lower.
We should be used to variability in this part of the world and unseasonable weather is the norm in the UK. What would we talk about otherwise?
The physical processes of the atmosphere mix cold air at the pole with hot air at the equator with the overall aim of evening out the temperature everywhere. Atmospheric thickness between standard pressure levels is the way the average heat content of the atmosphere is represented by meteorologists. Current situation is indicated in the featured image above.
Blue is thin, dense and cold. Orange is thick, rarefied and warm. One rule of thumb says that anywhere on the blue side of the white 528 line is subject to greater than 50% probability of snow/sleet in any precipitation.
Current UK weather is currently subjected to a cut off area of cold air being mixed down from the pole: meteorologists call this a cold pool.
Weather is a zero sum game: if there are losers then there are also winners. Note that Russia has relatively warm air being mixed north. Anyone to the north of Norway (North Cape to Murmansk) is enjoying unseasonably warm weather.