The seasons. Spring (March, April and May) is a time for sudden rain showers, blossoming trees and flowering plants. See Six reasons to love spring in the UK. Summer (June, July and August) is the UK's warmest season, with long sunny days, occasional thunderstorms and, in some years, heatwaves.Autumn (September, October and November) can be mild and dry or wet and windy.It's the season when the leaves fall from the trees and the temperature dips.ummer (June, July and August) is the UK's warmest season, with long sunny days, occasional thunderstorms and, in some years, heatwaves. Autumn (September, October and November) can be mild and dry or wet and windy.