Experimental Meta-Weather Rules

Weather. I've wanted a weather system that possesses the following qualities: is simple enough to be memorable, allows for the weather to be naturally and randomly changeable AND stay the same for long stretches, to show weather patterns/trends within a season and most importantly allow for the weather to become 'weird' so that the players can experience wild or dramatic weather phenomena (but not too often) and to try to do all this with as little die rolling as possible. With these criteria in mind, I tried to make a weather system that could achieve them. I don't feel entirely satisfied or successful with the result, the system is more complicated than I would like and janky at times. I am sharing for posterity as I think it's kind of interesting and for the RPG Blog Carnival. I'd love suggestions on how to make the idea that little bit more workable while retaining those design goals. There is a summary of the system at the end of this post.

(All shall be explained)

Find the other season lists here

The system works off of seasonal weather lists. They are 2.?D as opposed to hex-flower weather systems that are 6D.  This system is both more and less predictable than hex-flower weather systems. The weathers are arranged on the table from colder and wetter weathers to hotter and dryer ones. In hot/dry seasons like summer, the wet/cold weathers may not be particularly wet or cold and vice versa. Each weather should logically flow into the next, and the most common weathers will be found in the middle of the table. I have not strived for realism. Adjacent to each weather is a type of weird weather phenomena that could reasonably emerge from the mundane weather it is twinned with.

But how does it work? Place a marker on the current weather in your game (I used a matchstick) and, when you are asked to make a weather check, roll a d12. There are a number of possible results. On a result of 1-2 or 11-12 the current weather will remain the same. On a roll of  3, 4, 5 or 6 the weather will move one increment toward the wetter/colder end of the table, moving from a 10 to a 9 for instance. On a roll of 7, 8, 9 or 10, the opposite effect will occur and the current weather will move one step toward the warmer/dryer end of the table, IE from a 7 to an 8. If the weather cannot move up or down, i.e. is at 3 or 10, then the weather remains the same. 

Should the number that matches the current in-game weather be rolled, it indicates a sudden change. Roll the d12 again and change the weather to that result. If the new roll results in either 1, 2, 11 or 12 OR the same number as the current weather, then the weather will become weird. If the weather becomes weird, move the marker on the current weather one column to the right onto its matching weird weather. Once the weather becomes weird, roll weather checks as normal. Rolls of 1, 2, 11 and 12 results continue the weird weather. Weird weather is detailed a little more later in the post. 

But wait! There's more! In real life, over the course of a season there can be several periods of high and low temperature and dry/wet humidity. In order to replicate these kinds of weather trends I have once again gone META or more accurately (I think) extra-diegetic. Real world weather is taken into account when making weather checks using this system. The real-world weather the day of your game is used to modify the results of your in-game weather checks. The wetter, hotter, dryer or colder a day is compared to the average day of the season you are in, the wetter, hotter, dryer or colder your in-game weather will become. If a weather the day of your game is wetter/colder than usual; apply a -1 or -2 to your weather check, if the day is hotter/dryer than usual apply a +1 or +2. These positive/negative modifiers give the feeling of weather patterns. As a reminder, unmodified rolls of 1, 2, 11 or 12 always result in the weather remaining the same, but rolls that are modified into these ranges do not cause the weather to remain the same, simply changing one step in the relevant direction. Optionally, such rolls can cause the weather to change by 2 steps in the relevant direction. If the campaign is happening during the winter but being played in summer, this is fine. You can have hotter/dryer spells and wetter/colder spells relative to whatever season you are in in-game. 

But, what happens on game days where the weather is weird? When you have sessions on during heatwaves, cold snaps, hail, Saharan dust clouds, unexpected snow, eclipses? On such days the the probability of your in-game weather becoming weird increases dramatically. On 'weird' days, (until a weird weather results is procured) weather checks have the following results - on the roll of d12, a 1, 2, 11 and 12 do not result in the weather remaining the same but becoming weird, as does rolling the number that matches the current weather. As above, when making weather weird, move from the current weather to the right, onto the matching weird weather phenomena. On 'weird' days, the chance of the weather becoming wild or weird becomes 5/12. On normal days it is something like 5/144 (but I'm really not sure about the math for this). Once the weather has become weird, make weather checks as normal and is detailed above. 

How does weather stop being weird? Whenever the weather changes - moves up or down as a result of 3-6 or 7-10. Usually, the weather moves diagonally, up or down, to the mundane weather column. Many weird weathers will have lasting after-effects - such as flooding and wildfires.

I think that's everything. Here are the example seasonal weather tables. I haven't come up with mechanical effects for the different weathers as I am not sure of the viability of this system yet. I have rolled up a month's worth of summer weather using real-world weather data. I assumed one game session a week, rolling for three in-game days of weather per session. As you can see there are three different trends in this 30 period, a warm beginning followed by hot and humid weather in the middle of the month and then a dramatic week of thunderstorms. The bold days are when the weather changed as a result of a reroll and the Lightning Storm phenomena came about as the result of the influence of real world weird weather. 

Summer:

Here are some additional thoughts and optional rules:

• Seasonal weather tables can easily be turned into regional weather tables. Weather might be worse in the mountains, very different in a coastal deserts and rather peculiar in the worm-wastes.  
• It may be worth having a 'weather-master' or 'forecaster' player who is responsible for the tracking and rolling for the weather, just as you might have a mapper and caller. This would help to reduce your mental load. Some players enjoy such rolls and are all are motivated by a 100xp reward for doing them. It would also encourage the players to learn the weather system and become more experienced at forecasting like their characters would. 
• Mundanity is often necessary in fantasy role-playing games. Nothing seems as weird or special if the everyday baseline is already so foreign and removed from the player's lived experience. This applies to weather. Instead of a sun, having a neon-pink, glowing ball of tendrils might sound cool, but unless you mention it a tedious amount your players will forget about it. If the sun turns into something abominable for a week, that's cool and memorable. As a player, one of my best and most evocative memories of weather was when the party got lost in heavy rain in the middle of the night without any shelter. 
• Being very experimental, I would consider a weather phase during combat. Just as some rules have phases for magic, missiles, movement and melee there could be a phase for weather. This phase would see combatants deal with the weather and allow for the weather to act on and in the scene. For example; repeatedly prompting saves against heat exhaustion, seeing snow devils move around the combat map, see if a rain shower starts, how high the flood waters rise or where the lightning strikes. There are many options for weather to take more of an active and present role in combat encounters and the game as a whole.
• When to roll weather checks? That is up to you. Some roll them once per day, others integrate it into their wilderness encounter rolls/checks. I would have weather checks made at regularly times of the day - dawn, midday and dusk and once per day during downtime.
• The 'meta' aspect need not be limited to how hot/dry or wet/cold a day was. It can be linked to anything; windiness, amount of bugs you saw, how well you are feeling, how cloudy the day was. Having it solely based on comparative temperature/humidity limits excludes game-masters who live in equatorial countries. 
• These weather lists make for good rumour and spell fodder.

Summary:

Weather check:

• Roll a d12, considering the real-world weather, if hotter/dryer than usual add +1 or +2 to the result, if colder/wetter than usual -1 or -2 to the result. 
• Unmodified results of 1, 2, 11 or 12 result in the weather remaining the same. If modified into these ranges, treat the result as below;
• If the roll results in 6 or less the current weather decreases by 1 step. 
• If the roll results in 7 or more the current weather increases by 1 step.
• If the weather cannot move up or down, then it will remain the same.  
• If the roll results in a roll matching the current weather, roll the d12 again: 
• If 1, 2, 11 or 12 the weather stays the same.
• If the roll matches the current weather a second time then that weather becomes weird, moving to the right onto the adjacent weather on weird weather column. 
• If the d12 results in any other number, the current weather changes to the weather that matches that number.
• Once 'weird', the weather remains weird until a weather check moves the weather up or down the table. At which point the weather moves diagonally left, up or down, onto the mundane weather column. 

If the current real-world weather is unusual:

• Roll a weather check as normal. Results of 1, 2, 11 or 12 do not result in the weather remaining the same but becoming instantly weird. Likewise, rolling the number of the current weather causes it to become instantly weird.
• Once the weather has become weird, make all subsequent weather checks as is detailed above, even if the weather in the real world remains unusual. 

EXAMPLE SEASONS HERE