Monday will start pretty chilly with some early morning frost across Scotland, northern England and even south-east England. There'll be some showers moving southward across the UK with a lot of dry and sunny weather between. But, with a cool northerly wind developing on Monday temperatures across the UK will only be around 9 to 14C, falling short of the mid-May average of 12-17C. While temperatures may rise slightly on Tuesday, they will drop again from Wednesday onward. With the air coming from northern Scandinavia and the Arctic circle, temperatures will be around 3 to 7 C below average. Low pressure will become more dominant with some strengthening winds and showers. With the colder air in place those showers could be a little wintry with snow over the high ground of Scotland, which is not unusual at this time of year. Daytime temperatures will be around 9 to 14C and overnight temperatures around 3 to 6C, though it could be chillier in rural areas.…