Here's a house rule I've been fiddling with to add the risk of lightning strikes to the weather effects present in Song of Wind and Water.
After each player's turnover, before the next player starts attempting activations, roll one die. If the result is a 6, lightning strikes somewhere. Divide the battlefield into four sectors around the center, as shown below:
Roll one die again. If the result is 1-4, randomly choose a model in that region to be struck by lightning. A result of 5-6 means that lightning actually struck somewhere nearby. A model struck by lightning must make a quality roll on three dice. Even if the model gets three successes, it is still knocked down. Otherwise, check the table below:
1 failure: model is transfixed
2 failures: model is removed from game (normal death)
3 failures: model is removed from game (gruesome death)
Additionally, any models in base contact with the struck model are knocked down. Models defeated by lightning strike do not count for victory points.