v0.34:Temperature

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For temperature as it relates to choosing an embarkation site, see Climate.

Temperature scale

Temperatures in Dwarf Fortress are measured in the game's own, unnamed temperature scale, since termed "Degrees Urist" by the community. Temperatures in Dwarf Fortress are stored as sixteen-bit unsigned integers, which translates into a minimum value of 0 °U and a technical maximum of 65535 °U (2¹⁶-1), although this is internally limited to 60000 °U—60001 °U is used for temperatures which have been set to NONE. Floating point values are not considered, and when they appear any decimals are either sheared off or rounded away by the game. Urists are scaled logically against the Celsius scale, so conversions are simple, if non-intuitive:

[URIST] = [FAHRENHEIT] + 9968

   [CELSIUS] * 9/5 + 10000

   [KELVIN] * 9/5 + 9508.33

   [RANKINE] + 9508.33

Some reference numbers:

Significance	DF Scale	Fahrenheit	Celsius	Kelvin	Rankine
Boiling Point of Water	10180	212	100	373.15	671.67
Human Body Temperature	10067round	98.6	37.0	310.15	558.27
Freezing Point of Water	10000	32	0	273.15	491.67
Absolute Zero	9508round	-459.67	−273.15	0	0
Zero Degrees Urist	0	-9968	-5555.5	-5282.405	-9508.33

Values designated with round have been rounded internally to avoid decimals: for instance, the human body temperature is technically 10066.6, but has been rounded up to 10067 °U in the raws. Also interesting is the fact that temperatures in Dwarf Fortress can go far, far below absolute zero, which is physically impossible; considering Dwarf Fortress also allows perpetual motion, sometimes it's best not to ask questions. Temperature conversions are usually only useful when modding, and can be annoying to do manually; luckily a simple temperature conversion utility has been created for those who find themselves having to convert a lot of temperatures to and/or from degrees Urist often.

Examples of some temperatures encountered in DF, the most important ones in bold:

Event / location	Temperature
Alcohol freezes	09850 °U
Lowest survivable temperature	09900 °U
Outside, freezing climate (varies)	09960 °U
Underground, glacier ice	09990 °U
Water freezes	10000 °U
Nether-cap	10000 °U
Underground	10015 °U
Dwarf/human homeotherm	10067 °U
Outside, scorching climate (varies)	10080 °U
Tiles next to magma (warm stone)	10075 °U
Highest survivable temperature	10078 °U
Water boils	10180 °U
Material is fire-safe	11000 °U
Common stone melts (varies)	11500 °U
Items on fire (max)	11640 °U
Magma	12000 °U
Material is magma-safe	12000 °U
Creatures made of flame/fire	14000 °U
Dragonfire	50000 °U

Material values

Melting point

This is the temperature at which a liquid material will freeze, or a solid material will melt. In Dwarf Fortress, the melting point and freezing point coincide exactly — this is contrary to many real-life materials, which can be supercooled.

Boiling point

This is the temperature at which the material will boil or condense. Water boils at 10180 °U .

Ignition point

This is the temperature at which the material will catch fire.

Heat damage point

This is the temperature above which the material will begin to take heat damage. Burning items without a heat damage point (or with an exceptionally high one) will take damage very slowly, causing them to burn for a very long time (9 months and 16.8 days) before disappearing.

Cold damage point

This is the temperature below which the material will begin to take frost damage.

Specific heat

This determines how long it takes the material to heat up or cool down. A material with a high specific heat capacity will hold more heat and affect its surroundings more before cooling down or heating up to equilibrium.

Fixed temperature

A material's temperature can be forced to always be a certain value via the MAT_FIXED_TEMP material definition token. The only standard material which uses this is nether-cap wood, whose temperature is always at the melting point of water. If a material's temperature is fixed to between its cold damage point and its heat damage point, then items made from that material will never suffer cold/heat damage. This makes nether-caps fire-safe and magma-safe despite being a type of wood.

Due to the way fixed temperature is handled, giving a material a fixed temperature will not cause its actual temperature to change accordingly — instead, its temperature will simply be permanently locked at whatever it was previously. Removing a material's fixed temperature, however, will cause all items made of it to heat or cool until reaching equilibrium with their surroundings.

The fixed temperature of a container does affect its contents, but you can't freeze water by putting it into a bucket made from nether-cap because water will not freeze until it cools below 10000 °U .

The fixed temperature of an inorganic material has no effect on unmined walls made from that material, though boulders will take on that temperature as they are produced via mining.

Bugs

• A calculation error causes objects in containers to maintain a 1 degree difference from the container, resulting in constant recalculation.^Bug:6012 DFhack provides a tweak to stabilize the temperature of such objects.

• Temperature calculations have a significant impact on game performance. (Temperature calculations can be disabled in the D init.txt file.)

• When temperature calculations are disabled, dwarves will refuse to set foot in a cast obsidian tile (or other tiles previously occupied by magma).^Bug:6033