You might have heard that we in the Pacific Northwest have been buried under a surprising amount of snow. That got me thinking about how most RPG adventures assume good weather (or at least no weather of note), but the reality is we sometimes experience downright bad weather. That's something to keep in mind during your adventures, whether you're running them or writing them. From a narrative perspective, weather can often help set the mood.

Now, most games have some weather-related rules in the rulebook, but they are often either (a) fiddly and hard to remember ("hey, did you remember the -2 to Perception checks because of the rain? And, wait, your torch has a percentage chance to have blown out by now.") or (b) overwhelmingly punitive ("oh, looks like the snowdrifts here mean you can move one square each round. If you run."). I think there's a better way to do weather.

The best type of weather effects are easy to apply in specific circumstances that matter, have game mechanics that are easy to remember, and have a memorable and sensible impact on the narrative of the adventure. That is, they aren't relevant until the story makes them relevant. Here are some examples.

* Early on, the GM lets the players know it's a foggy evening, a misty moor, or what have you. Maybe they have a penalty trying to shoot a bow at someone far away, because of the mist. But when the heroes later get jumped by a vampire in the street, they defeat it...only to find it turn to mist and become effectively invisible in the fog. The heroes must do some more legwork!

* Snow is coming down and starting to stick to the ground. It's not enough to cause any game mechanics yet, but the players with good Survival know it will get worse. Later, the heroes must track a kidnapper through the thickening snow. Their overland speed is halved from the snowfall, but they have to hurry because in a certain amount of time, their speed will be halved again, and the kidnapper will certainly get away. In a cabin they pass, they can find snowshoes or skis, which eliminate the movement penalties and allows them to catch up.

* It starts raining quite hard as the heroes travel to a baron's hunting lodge, and perhaps some poachers that attack them on a muddy forest road must deal with difficult terrain. Later, when the heroes are trying to find out which guest at a baron's hunting lodge is a murderer, it's the guest who's been at the lodge the longest--and they might realize it's the one whose coat hasn't gotten wet.

* In fantasy worlds, weather can be overtly magical. A rain of tiny, glittering crystals might cause capricious fey creatures to cavort in the rain, either causing trouble or being available to help the heroes. But such a rain might cause invisibility effects to fail due to the glittering crystals.