Really Neat Tricks: Weather in the Mouse Guard Role Playing Game

Let's take a look at the Mouse Guard RPG's seasonal weather system. This post leads a series presenting rules, design elements, lore, and concepts that I've found handy beyond the game that they first appeared in. In this case, it's a system that adds weather as an element to a fantasy campaign without needing a meteorology degree.

I'm not usually one for nostalgia, but I miss RPG boxed sets.

The system is built around the idea that weather is a significant obstacle in the Mouse Guard setting. This makes perfect sense in Mouse Guard - the player characters are literally mice. Small mammals would be effected by even minor weather changes.

Adapting the system to other fantasy games brings in an often ignored element. Seasonal weather can present both challenges and opportunities to an adventuring party - spring storms slow travel, supplies are easier to come by after harvest, winter tends to shut everything down as snow and ice block traffic, etc. I'm guilty of overlooking weather unless I want to add atmosphere to a roleplaying interaction or spice up a combat encounter. If nothing else, adding a mechanic for handling weather adds variety to a fantasy campaign.

Mouse Guard's system for modeling seasons and weather takes up a whole chapter, so this is a bare bones summary. The gamemaster determines how many game sessions each season of the year will last, ranging from one to three sessions. An alternate system triggers a seasonal change based on how many times the gamemaster bring weather into play. In either case, the change of the seasons is inevitable.

Each season is described in its own section - animal activity, the kinds of weather that can be expected, conditions in the wilderness, and the kinds of adventures and other activities that are available for the player characters to pursue. Mouse Guard is set in a temperate zone, so winters are long and the other seasons tend to be short. Spring is a busy time, but rain and mud can slow things down. Summer is unhurried, but productive. Fall is another busy time as the harvest is brought in and everyone prepares for the coming cold. Everyone hunkers down during winter - player characters in Mouse Guard use the time to rest, recover, practice, and engage in role playing.

The system can be modified for other climates or for changing conditions. The next campaign does not take place in a temperate zone? Alter the length of seasons and the types of weather generated. Is the big bad cult gathering strength, summoning dark powers in the north while weakening the deity of fertility? Gradually make the winter longer while shortening the other seasons through years of game time. Food gets more and more scarce. Trade is disrupted. Armies can't get around fast enough to respond to reports of a new threat from the north. It's up to a plucky band of adventurers to find the cause and fix the problem before the final winter comes.

Mouse Guard's seasonal weather system avoids a couple of problems I've seen in other weather generation mechanics. First, it does not require the record keeping of a detailed calendar. Creating a calendar for a fantasy world is a daunting task - how many days in the year, what to name the weekdays and months, how do the phases of the moon(s) line up, where do the holidays fall, etc. Keeping up with it is even more work. Mouse Guard sidesteps the issue by basing seasonal progression on the number of sessions played. Second, it does not try to be a weather simulator with tables for wind speed, air temperature, humidity, etc. Is the weather close enough to maintain verisimilitude and how does it effect play are my concerns as gamemaster. The precise air temperature and number of inches of snow matter less to me than is it cold enough and is the snow thick enough to make even Conan the Cimmerian reconsider his travel plans and settle by the fire for some mulled wine?