1) Lightning does strike more than once.
2) Schwartz's Law: The observed snowfall exponentially decreases according to the amount of time spent discussing the expected snowfall and the general excitement of the group conducting the discussion.
3) Consensus (the average of all independent forecasts) is tough to beat.
4) The laws of thermodynamics: (i) you can't win, you can only break even; (ii) you can only break even at absolute zero; (iii) you can never reach absolute zero.
5) Forecasting thermodynamics: (i) you can't win, you can only break even; (ii) you can only break even if no weather is happening; (iii) weather is always happening.