A couple of photos from my house on 19 June 2005. After a hot (28 C ?) sunny day the sky got increasingly black during the afternoon as a thunderstorm approached from the south west. This photo shows the darkening sky, there was constant distant thunder and a gusty wind getting up but no rain yet.
By 1620 it was so dark the street lights came on and there was lightning in all directions - several flashes a minute, though most were some miles away. Thunder was constantly echoing round the hills, then the heavens opened...