I'm really into weather and climate so this excites me to see hopefully a decent representation of UK's climate in a video game as there is often a lot of variation between small distances that the national forecast is only good for a general picture to get the idea of the air streams.
You need to understand actual ocean conditions for them it's the NAO (North Atlantic Oscillation) to figure out what the phase means for the weather and why they are 'stuck in a rut' patterns both wet and dry ruts that lead to long periods of such conditions. Such as the 1976 drought or the 1985 cold snowy weather period,etc or the late 90s/early 00s mild and wet winters though I think those were an unique horse of a different color.
PS. There's info about the map revealed here though it's only a concept map but it looks like a lot of geography is happening here. https://www.youtube.com/watch?v=o8kP-pBYPgM
there doesn't seem to be anything here