To celebrate Valentine's day, let's take a look at the romance-themed episode of the Simpsons!
In the Season 6 episode 'Another Simpsons Clip Show', Lisa flashes back to 'I Love Lisa', and her hilarious misadventures with Ralph. As she narrates the opening scene of the flashback:
Lisa cheekily comments that "it was an unusually warm February 14th, so the children walked home without jackets". It seems the writers noticed a plot hole in the episode, and decided to call it out.
One problem, though - it's not actually a plot hole. You see, 'I Love Lisa' took place six episodes after 'Mr. Plow'. And how did that episode end?
That's right, with God intervening to end winter in Springfield that year, specifically to foil Homer and Barney's plans to go into business together. So of course there wasn't any snow come Valentine's Day. If nothing else, The Simpsons' God knows how to hold a grudge.