Nary a snowflake up north here, but you know who to thank for snow fun! (JFrost....I believe) TGIF!!!
It's to honor all the saints at once and catch all the ones who didn't get their own feast day. Which, seriously, almost every day is somebody's feast day.... All Souls Day is the next day, to honor all the non-sainted daed people and (if one leans toward Purgatoial beliefs) pray for them to get out of Purgatory and into Heaven. (Basically, the Church couldn't stop the old celebrations of honoring the dead, so it incorporated them.) This has been your religious explanation from the recovering Catholic. I'm currently sitting here waiting for the last of my candles to go out for my own dead people celebration. Only two left.