User Tools

Site Tools



Mapcraft - Fantasy map designer

WorldGen - SciFi universe generator

Mapcraft Web - Web based fantasy map designer

All code for the project is released under the GPL, and is copyright Samuel Penn.

The text on this wiki is dual licensed CC-BY-SA and GPL.

You can contact the author at



The temperature of a planet is a rough estimate of the average across the entire surface over the course of a year. For ease of description, a world is given a descriptive rating based on how suitable they are for human habitation.

Winter Worlds

Extremely Cold

At 200K (-73°C), the average temperature is considered close to the coldest arctic conditions on Earth. Life may exist around thermal vents, but there aren't any sufficiently warm periods for life to flourish globally.

Very Cold

With an average surface temperature of around 230K (-43°C), such worlds are considered uninhabitable. There is no liquid surface water, though under-ice oceans may exist. Plant and animal life is limited to the very small and simple, and the polar regions tend to be barren of all life, dropping below 180K (-100°C) for much of the year.

Habitable Worlds


Cold worlds have an average surface temperature of 260K (-13°C). They are snow covered worlds, with no surface water. Living on such worlds is hard, but possible with the right training and gear. Large land animals don't exist, and any vegetation is extremely adapted to the cold.


Cool worlds are colder than the Earth, with an average temperature around 280K (7°). Polar ice caps tend to be extensive, but equatorial regions may be clear of ice. Alternatively, the world may be covered in snow and ice, but water will be accessible beneath the ice sheets. Vegetation will be sparse, but there may be plenty of life in the oceans.


A standard Earth-like world, with an average temperature around 290K (17°C). These are considered ideal. May have polar caps and hot deserts and rain forests.


Warm worlds are hotter than Earth, around 300K (27°C). They generally lack polar ice caps, and depending on the amount of surface water may have extensive deserts or steaming jungles. Their northern and southern latitudes will be pleasant, but violent storms may be common.


Hot worlds have an average surface temperature of around 320K (47°C). They never have ice caps, and large parts of the world will be uninhabitable due to the heat. Equatorial regions may have surface water which is at or near boiling point. The seas may contain high levels of dissolved metals that make it undrinkable for humans without filtration.

Large animals tend not to be native to such worlds, and plants and smaller creatures tend to be well adapted to the heat.

Temperature Kelvin
UltraCold 50
ExtremelyCold 100
VeryCold 200
Cold 250
Cool 273
Standard 293
Warm 310
Hot 330
VeryHot 360
ExtremelyHot 400
UltraHot 600

Standard is about the only sensible temperature for human life.

Cool worlds will have some hospitable areas, and will probably have liquid water in places if there is an atmosphere. Surviving will be a challenge however.

Warm worlds can be of two types - wet or dry. Dry worlds are generally deserts, though liquid water may be plentiful life will be limited to a few wet areas. Wet worlds will be steamhouse jungle worlds with no ice caps.

Cold worlds are snowball Earths or worse, with no liquid surface water. They are unlikely to have much oxygen, and only the simplest life forms (lichens, bacteria) will be present.

Hot worlds are barren, desolate worlds. Any oceans are likely to be small and dead.

worldgen/planets/temperature.txt · Last modified: 2017/12/03 18:12 by sam