Random Climate & Terrain Generator

I’m dearly fond of random generators for things in tabletop rpgs because the results are often so interesting, it avoids any sense of staleness, and it dispenses with the usual decision fatigue if I’m in a pinch or need to toss out something very rich very quickly. I have way more of them than you might expect, and in extreme detail. Some day soon I’m going to release a pay-what-you-want DM helper that will contain all of them, but as I clean them up so that they’re readable by people other than myself. My pride and joy is my 35-factor Random Personality, Culture, & Backstory Generator, which is also the basis for how I analyze personalities. That’s how I make people. This is how I make places.

In the beginning, make the heavens and the earth.

Whether you do terrain or climate first doesn’t actually matter. I prefer to do climate first, mostly because that’s the order in which I wrote the tables.

Seasons

If you want to be orderly, roll 1d5 for the primary axis of seasonal shift in your area, then roll 3 ternary dice (a d3 or d6 with the outcomes -, 0, and +), 3dT to determine the degree of displacement. There’s nothing stopping you doing this many times, or even making 2 rolls on each axis.

Roll	Axis	Ends
1	Temperature	hot/cold
2	Precipitation	dry/wet
3	Bounty	bloom/ebb
4	Wind	still/gusty
5	Day length	light/dark

If you want to be more fun, first decide how many seasons you have ^{unless we’re playing by Song of Ice and Fire rules} by using one of my advanced rules for table construction. The longest I’d want a season to be is 6 months, so our table will run from 1-6. Then I’ll put alternating weights on them, and finally tally how many that is.

Length of the season	Weight	Die range
1 month	1	1
2 months	3	2-4
3 months	5	5-9
4 months	6	10-15
5 months	4	16-19
6 months	2	20-21

Now I happen to have a d14 and a d3, so I can use a virtual base system to roll that easily. Since most people don’t however, you can pull one out of the 5 month section, so that it reads 16-18 and the 6 month section is 19 & 20.

That method of on-the-fly table generation is a variation of the Magnitude Table that I use for generating things like the value of rewards or the ages of countries. We’re about to do it again to determine how many seasons we have.

Number of seasons	Weight	Die range
3 seasons	5	1-5
4 seasons	4	6-9
5 seasons	3	10-12
6 seasons	2	13-14
7 seasons	1	15

If you roll high, determine what they are first, arrange them in an overlapping fashion. A mundane example of a 5 season cycle is cold => wet => bloom => hot => ebbHarvest => cold.

Predictability

How stable is the weather in this area? Roll 1d3 to generate an outcome list for the next part, and feel free to make more entries or lopside the current ones as you see fit. For bonus points, reroll this for each season you just made.

Roll	Predictability	Outcomes
1	Mild	-1,0,0,0,+1
2	Temperate	-1,-1,0,+1,+1
3	Trecherous	-2,-1,0,+1,+2

On an axis of 4 (good, fair, bad, extreme) or 5 (add moderate betwixt fair and bad) roll 1d5 and read it according to the outcome list in the predictability table to generate the current weather state.

Alternately you can use different combinations of dice. A roll of 2dW is a roll of 2 ternary dice used to generate a wellcurve instead of a bellcurve ^{see upcoming Curves & Table Construction}.

Roll	Predictability	Outcomes
1	Mild	2dT
2	Temperate	1dT
3	Trecherous	2dW

These are as much for creating places as they are for playing them, so I’m including my tables for daily changes as well. The first of these is of course the predictability table, but that also has other uses so I didn’t put it in this section.

Wind

Roll 1d12, where 1-9 are as a keyboard number layout, 5 is calm, and 10-12 is no change. For seasonal winds, roll 1d9 to be read the same way. Here’s a table, for people that can’t visualize things.

10 NC	11 NC	12 NC
7 NW	8 N	9 NE
4 W	5	6 E
1 SW	2 S	3 SE

Alternately roll (1d5)d4 or an appropriate number based on the Predictability table, then add them together on the following chart to find a direction and magnitude.

–	1 N	–
4 W	–	2 E
–	3 S	–

You can also roll 2d4 on this table to determine variations in the prevailing wind, if you chose that route above. Rolling towards the prevailing wind means it got stronger, rolling against means it got weaker, and the other 2 are deflections to one side or the other, which makes this table significantly more useful for sailing.

Terrain

I had the pleasure of doing everything else with markdown. This will be a bit of a mess. Roll 1d12 on the following table, or select your favourites, apply weights, and make a smaller table. I frequently refer to this section at the beginning of a game when I haven’t decided where to set it yet, which is why some of the options are odd.

Roll	Terrain	Subtable
1	Cave	1 Caverns 2 Mines 3 Catacombs 4 Sinkhole
2	Woodland	1 Deciduous Forest 2 Coniferous Forest 3 Jungle
3	Plains	1 Shortgrass 2 Tallgrass
4	Island	1 Single 2 Atoll 3 Archipelago 4 Chain
5	Mountains	1 Ridge 2 Cliffs 3 Volcanoes
6	Valley	1 Fjord 2 Great Crevasse 3 Mountain Valley 4 Canyon
7	Desert	1 Sandy 2 Arctic 3 Rockflats 4 Parched earth
8	Hill	1 Rolling/dunes 2 Mesa 3 Buttes
9	Wetland	1 Swamp 2 Bog 3 Bayou 4 Moors/fen
10	Urban.	See the upcoming Civilizations document for a series of generators
11	Sea	1 Tidal zone 2 Shallows 3 Reef 4 Continental shelf 5 Open blue 6 Abyssal Plain 7 Trench
12	Cloud	There was a table for this once, but it was made of paper for a specific campaign setting and has succumb’d to the ravages of time. I’ll make a new one at some point.

Add an 8^th option to Sea in the middle for Deep Blue, or the twilight zone, if for whatever reason you’re going by depth instead of how far beneath you the water stretches.

Note that you can use 1d12 for this, or eliminate cave & cloud for 1d10, or leave cave but merge island and sea for 1d10 again. The way I roll this table is similar to my Random Dungeon Generator, usually just looking at the top level prompts and making it more specific on a second pass. I’ll roll for a central area, note it into the middle of the page, then make additional rolls for each of the cardinal directions and so on, filling in space until I’m satisfied, then redrawing the actual features in and deciding how they mesh together. Generally I vary climate on larger distance scales than I vary terrain, and only a feature or 2 at once unless the change in environment is dramatic.

Elevation

Roll the following with 1d10.

How high	Weight	Range
Below sea-level	1	1
At/Near sea-level	3	2-4
Moderate	3	5-7
Highland	2	8-9
Very High	1	10

You can also make it 8 choices rather than 5, adjusting the weights accordingly, and add underland, deepland, and farland.

For smaller areas, I like to make charts that approximate elevational isopleths by using the ViHart method of optical-illusion-y spiral making by starting a spiral with a wonky shape and exaggerating bumps and variances in it as you go around it. That’s great by itself for a mountain or something, but to get more interesting terrain you need to randomly place dots and lines that will serve as local maxima, then branch your spiral out to them as it fits, otherwise you always wind up with a not quite round warbally blob like a pruny fingerprint. Since the line is a spiral and not a series of rings, it isn’t a true isopleth topological map, but you can easily break the spiral into rings in a revision pass if you really need to.

Eventually I’ll redo the terrain section to follow actual science like my Personality Generator, what’s up there was just stuff I thought up off the top of my head in a hurry because I tend to make these generators in the moment I need them.

Edit: Add’d a few links now that my Personality Generator is up. If you’re only making a place, the culture section is great for establishing the default mindset of a civilization, and just below that is a table you can adapt to use for a country’s age, and if it’s a fantasy game or story the race section can give you unique inhabitants.