Working Out Climates Using the Climate Cookbook


There’s a bit of a disclaimer on this weeks post which as promises is on working out climates. I appologise, but my knowledge on this subject is pretty limited and after researching it became apparent that there was one main resource for this which is Geoff’s Climate Cookbook. Instead of parroting this back to you, I encourage you to give it a read and apply it to your world. All credit for this technique goes to him.

So what I will be doing this week, is applying it to my world and talking through this process and the results. I hope this will be useful, as I found the Cookbook rather confusing to apply so this should make it clearer for those attempting to have a go. We will return to normal guides next week, with a guide on something I have developed myself.

This post will therefore function as a simplified tutorial and a walk through of working out climates. This is a complex subject, but if like me, you want to create a world with a basis in reality, enjoy the wildcard of following methods like these to create a world where even you don’t know exactly where you’ll end up, and don’t mind about it 100% factually correct, then this guide will be for you.

When following this, use a program such as Photoshop or GIMP (or tracing paper) and keep each different thing on a separate layer or it might become a bit of a mess.

The Start


This is the map I will be apply the climate to. It is a rework of the map I was currently using to build my world (not the one from last week). For this process, you will need your map showing landmasses and you need to have your mountain ranges shown on the map.

Default Winds


The first step is split your map into thirds (or 6 parts if you are making the southern hemisphere too), adding the winds as shown. These winds are what would occur if there was no landmasses on the planet. The three annotations are the pressure zones, Polar Front, Sub Tropical High Pressure Zone and Inter Tropical Convergence Zone.

High and Low Pressure


Next you want to work out your areas of high and low pressure. In winter, the cooling of the ground causes high pressure, leaving low pressure areas over the ocean. In summer, this is reversed. In winter, the high pressure zones stretch out across the STHZ, in summer the low pressure stretches out across the ITCZ and PF. You may choose to accent this more than I have. My areas are largely water across these lines so I chose not to.



This is where it starts to get a bit tricky. You need to work out your wind deflections across your map. In the northern hemisphere, in winter, winds are deflected clockwise around high pressure zones, and anti-clockwise around low pressure zones. In the southern hemisphere this is reversed. In summer, this is all reversed (so in the north, winds are deflected anti-clockwise around high pressure and clockwise around low pressure). Remember you are deflecting from your default winds (the white arrows).

Ocean Currents


The next step is to work out your ocean currents. These can also be a bit tricky. The high pressure of the STHZ causes a different result to the south and north of it. Above it, warm currents flow to the west side of landmasses, south to north and cold currents flow to the east side, north to south. Blow the STHZ line, cold currents flow on the west and warm on the east. This is all reversed for the southern hemisphere. These currents tend to make circular patterns as you can see above as water heats and cools. Also try to follow your wind currents from the previous step.


This is where things begin to take shape (and can be a tad confusing). Remember here precipitation includes snow, so don’t get stumped if you have high precipitation in the regions you were expecting to be snowy wastelands. Paint on two colours, representing high and low precipitation. These are relative and will be made more specific later on.

First look to your mountains and the surrounding winds. Mark high precipitation on the windward side, and low on the opposite side. Next to ocean currents. Warm currents will result in high precipitation and cold currents, low precipitation. Onshore winds cause high precipitation and offshore or parallel cause low precipitation. You might already have much of coast accounted for from applying the effects of the currents, so when doing the winds, these lines might be more inland than the effects of the currents.

After applying these you should have two rings around the coasts of your landmasses, on the outside, for ocean current effects and on the inside, winds. These may both high or both be low pressure. You will also have have precipitation levels around your mountains. For small  islands, I applied their levels based on the ocean currents, or if didn’t have any near them, the wind levels.

There may not be loads of land left to cover, but interiors on our larger landmasses that are not near mountains should still need looking at. Along the STHZ these are low precipitation areas, and high precipitation along the ITCZ. Then for remaining interior areas, mark extreme interiors as low precipitation and high for western coasts subject to the PF and someway inland.


The result may be something like you see above, where darker brown indicates high precipitation and lighter indicates low precipitation.


Now you get to do it all over again, but for summer! Remember to flip the instructions. This will result in a different set of wind patterns, which lead to different ocean currents and ultimately, different rain patterns.


So after running through it for summer, I ended up with this. Don’t worry about what you’ve ended up with, whether there’s too much or not enough rain. You can always adjust it as you see fit later.


Next divide your map up into 9 equally spaced sections. These are to help you work out your latitude. My landmass goes off the edge of the map in the north and I wish for this to be an unknown icey region, so I have divided my map into 8 regions as anything above 80 degrees in latitude will be an icesheet. Working from the bottom up, my equator upwards, each line represents 10 degrees. To work out your southern hemisphere, do the same, working from the equator down.

You should also have a general idea of how a height map of your world would look. I am generally assuming there are hills around the mountains and gradually flattens out towards the coast.

Discovering Your Climates

Use the following table to figure out your climates. I found it easiest to look at the location first, then the level of precipitation and this would tell me the climate and therefore the temperature.

  Temperature Precipitation Location
Name Summer Winter Summer Winter latitude in degrees
Tropical rainforest Hot Hot Wet Wet 0-10
Tropical monsoon Hot Warm Very wet Short and dry 5-15; east and south-east coasts only
Savannah Hot Warm Wet Long and dry 5-15
Hot desert Very hot Warm Dry Dry 10-30, especially on west coasts with cold currents
Hot steppe Hot Warm Low to dry Low to dry 10-35; typically next to deserts
Cold desert Hot Cold Dry Dry Interiors, rain shadow
Cold steppe Warm Cold Low to dry Low to dry Interiors, rain shadow
Maritime east coast Hot Warm to mild Wet Moderate 20-40; east coasts only
Maritime west coast Warm to mild Cool to cold Wet Wet 40-60; west coasts only
Mediterranean Hot Mild Dry Moderate 30-45, west coasts only
Temperate monsoon Hot Mild to cold Wet Dry 20-40; east coasts only
Laurentian Warm to mild Cold Moderate Low 40-60; not on west coasts
Subarctic Mild to cold Very cold Moderate Very low 60-80; not on west coasts
Manchurian Warm to mild Cold Moderate Dry 40-50; east coasts only
Subarctic east Mild to cold Very cold Moderate Dry 45-70; east coasts only
Tundra Cold Very cold Low Dry 60-80
Icecap Very cold Very cold Low Dry 75+

If you, like me, find this table is a bit overkill. Consider using this simplified table below.

Temperature Percipitation Location
Name Summer Winter Summer Winter
Tropical Hot Hot Wet Wet 0-23
Savannah Hot Warm Wet Long and Dry 15 – 30
Desert Hot Hot Dry Dry 0 – 30
Steppe Warm Cold Moderate Dry 50 – 60
Temperate Warm to Mild Cold Moderate Dry 23 – 65
Taiga Cold Very Cold Moderate Dry 50 – 70
Tundra Cold Very Cold Low Dry 60 – 80
Icecap Very Cold Very Cold Low Dry 75+

So using my slimmed down table, the results was as follows.


These colours represent the following:

  • White: Icecaps
  • Grey: Tundra
  • Blueish: Taiga
  • Light Green: Temperate
  • Dull Green: Steppe
  • Dark Green: Rainforest
  • Red: Desert
  • Yellow: Savannah

If you want to make your world 100% accurately, feel free to stop there, otherwise you may want to change the world to suite your own plans.

Artistic Direction

My preferred method of worldbuilding is to use methods like this and like using tectonic plates to figure out how things would look if they were developed naturally, and then change the results to suit how I want them. On this map, I want the south border of the map to be a desert that extends off the map, a hot barren place where people don’t go and people aren’t sure what lies on the other side, if anything. I want the big centre temperate forest to be an exotic jungle called the Deep Woods. I also feel there is a bit too much steppe environment on the map. My island chain in the south ended up as all desert, which I thought was rather boring, so I changed them up too. Make your changes as you see fit. The joys of worldbuilding is that you are in control, you can do it how you like! But I like using methods like this to provide a realistic guide. So I ended up with this.



So hopefully you enjoyed this and found it useful and I appologise it wasn’t an original tutorial. Next time, I’ll be explaining something I’ve developed myself, Resource Maps. This will help determine how our nations grow and how trade will develop, which will greatly impact the fortunes of your nations.


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