Though weather is mentioned a few times in various circumstances, there is no weather table. The closest I've found is the wind-speed table for ships, which is a step in the right direction, but doesn't tell me much about thunderstorms, tornadoes, blizzards, and other such weather phenomena.

That said, I've created a few tables to help out. Roll 1d20 for the appropriate season and location (Polar is arctic conditions, Tropics straddle the equator, and Temperate is between the two) to get precipitation:

  Spr/Fall Summer Winter
Polar 19+ 19+ 19+
Temperate 13+ 15+ 17+
Tropic 19+ 8+ 19+

Roll 1d20 to get temperature:

  Spring Summer Fall Winter  
Frigid 1 -- 1 2-6 Thick ice on rivers and lakes; move 1/2
Cold 2-6 -- 2-6 7-14 Thick ice on lakes, thin on rivers; movement 1/2
Cool 7-14 1-6 7-14 15-20 Above freezing
Warm 15-19 7-14 15-19 -- Comfortable temperature
Hot 20 15-20 20 -- 2x water consumption, movement 1/2

For Polar, shift one step cooler (Warm becomes Cool); for Tropics, shift one step warmer (Warm becomes Hot).

Finally, check the chart below to see what weather occurs:

  No Precipitation Precipitation
  Calm-Str. V.Str. Gale Calm-Avg. Str. V.Str. Gale
Frigid Clear Blizzard Blizzard Snow Blizzard Blizzard Blizzard
Cold Clear Blizzard Blizzard Snow Blizzard Blizzard Blizzard
Cool Clear Windstorm Tornado Rain Sleet Deluge Tornado
Warm Clear Windstorm Tornado Rain Storm Hailstorm Tornado
Hot Clear Windstorm Tornado Deluge Rain Storm Tornado

Windstorm/Blizzard: in desert or snow-covered, vision is reduced to 20' and archery is impossible. Movement is reduced by half. Tornado: along with weather from Very Strong Wind, there is a tornado, moving with the wind at 240'. Clear/Rain/Sleet/Snow: regular weather. Deluge: vision reduced to 20'; causes floods 10'/turn in valleys. Storm: vision reduced to 60'; chance of lightning strikes. Hailstorm: Anyone not under cover is hit with hailstones (as 2nd level fighter, 1d2 damage, every round).

Roll temperature once per week, wind once per day, and precipitation 4 times a day (morning, afternoon, evening, night).

This is just a rough draft... it seems to work ok, but it's an awful lot of rolling, and I'm not sure about some of the percentages. That, and it's possible to get sleet in the afternoon and an overnight tornado. And speaking of tornadoes, they, along with blizzards, storms, and frigid temperatures need fleshed out more - some way to handle the massive damage they dish out, but at random.

There was a Kingdoms of Kalamar book that had some great weather tables that yours remind me of, so I’m not sure if you’ve seen it or not.

This post is even less helpful because I don’t remember the title or have time at this moment to look it up, but if you squint real hard and pretend, I was almost helpful!

(Anyway I really like having random weather determination available to me for sandbox play, because weather can affect exploration so much, so I like this thread.)

The sad truth of why there are no climate tables in ACKS:

Waayyyyy back when I first conceived of the Auran Empire setting, more than 10 years ago, I initially mapped it by horizontally flipping the Mediterranean and then moving pieces around. In my youthful ignorance I did not realize the dramatic effects that horizontally flipping the Eurasian land mass would have on the climate of the region. I just essentially kept the climate as it was.

Creating a more realistic climate for the Auran Empire setting has essentially taken me from then to now (and in fact I still tinker with it). With the climate changing (hah) I haven't yet written the tables for the various regions.

 I think you are moving in the right direction with your rules set. It's just a matter of how complicated you want to make it from there.

We need weather tables. A good article would be great to include in Axioms. I remember being very interested in the Greyhawk weather tables in one of the campaign books, but it was quite complex if I recall.

As to the notion of a lot of dice rolling, I remember the Greyhawk weather notes suggesting that you roll weather for a long period of time (such as a week or month) in advance.

I’ve considered, but not yet added a table for a few basic ideas. At some point in the temperate zone, each season had equal status. From there, every X hexes north starts spring one week later, and every X hexes south it starts a week later. The number of hexes X should coincide so when you reach the tropics, there is no winter, and when you reach the arctic, there is no summer. At one point I had that number figured out, but I seem to have lost it in my notes…

Mountains shift one zone cooler (tropic mountains are considered temperate), and deserts only ever get rain on a 20. Tropic ocean hexes have reversed rainfall chances from land - more rain in the winter, little rain in the summer.

I would suggest rolling at least a week of weather at a time, since each week has the same temperature range.

The big thing this doesn’t cover is per-hex weather… Right now, I only roll for the hex the players are in, and apply it to most of the region. It could probably be expanded quite a bit to include weather moving from one hex to another, how land affects it, and so on - but that may be more information than I’m willing to deal with. Heh.

This reminds me of a more generally useful piece of worldbuilding I have wanted for some time, but am not savvy enough to design myself, would be a set of quick hints for building a world out from an established point based on what you've already said is true.

For example, if you declared the player's starting town is on a river, flowing out one end of the town and in the other, you know traveling upstream will eventually lead you to higher ground and possibly mountains, while traveling down will get you to a body of water. once you know the body of water and what you said the town was like (arid vs. wet) you then know which way the wind is blowing, which could tell you roughly on an earth sized globe what lattitude it might be.

Most weather patterns (at least for an Earth-like planet; you're on your own for non-Earth-likes) can be reduced to a fairly simple formula based on lattitude, altitude, and distance from oceans and mountains; if you can get wind and precipitation down, you've got most of it handled. I'm sure such a formula exists, with varying levels of complexity; I just don't have the background or the time to figure it out.

That, and at a certain level of complexity, this stops being a pen-and-paper game and becomes a computer game!

Strictly speaking, as a computational engine myself, all games I play are computer games. *insert thufir hawat gif*

Where weather and climate become truly tricky:

  • Horse latitudes - desert almost regardless of other factors
  • Tropics - seasons vary dramatically in length and effects
  • Altitude - hotter and drier the lower you go; Ethiopia is a really interesting study of how altitude plays with latitude to achieve some surprising results
  • Monsoon effects
  • Micro-climates - Sequim, Washington, or the Rhine Valley are both examples that spring to my mind
  • The real fun one: a non-Earth-like world; for example, because Mars has a very elliptical orbit around Sol, you might argue that in its middle latitudes, it has more seasons because the varying distance to Sol really impacts weather