Lyric discussion by nickdon72 

Cover art for Die In The Summertime lyrics by Manic Street Preachers

in english literature the seasons can be used as metaphors for times of life i.e. spring= infant summer= adolesence autumn= middle aged etc. so here richey is saying how its best to die when your young so at least the life you left was full of happy memories instead of waiting to winter where its a different story. quite similiar to the ideas in suicide is painless.