Meteorologically speaking, this is the last day of summer. This is purely for statistical purposes, the Met Office divides the year into convenient three-monthly 'seasons' to make the analysis of statistics easier to manage. To many though, the summer finishes at the equinox - which is on 22nd September this year (at 15.21to be exact). From this date the nights are longer than the days.
Of course 'the weather' wouldn't lower itself to be constrained by such arbitrary dates. 'Summer' weather can occur well into September and sometimes into October as well, just as Autumn and indeed 'winter' weather can sometimes occur in 'summer'. It all depends on how the jet-stream shapes up and where our winds originate.
One thing is for sure, the nights are drawing in, currently we are currently losing around five minutes of daylight each day. As a result nights are longer and early morning mists will be more likely. Looking towards this weekend, the weather is turning wetter with potentially some spells of quite heavy rain coming through later on Saturday and again Sunday night into Monday. As always, things can change so keep up to date with the very latest forecast.