Temperature and ice

The air has a temperature wherever you are, and the pause menu (Esc) tells it, as 4 °C (or in °F; see Settings). For now the cold does nothing to you; what it does is freeze water.

Underground

Dungeons are cool and steady: 10 °C unless a place is colder or warmer, the same day and night, whatever the weather outside. Deeper levels may be a little colder, and some places are below freezing.

A special room may be hotter or colder than the level around it. A sweltering chamber is 25 °C warmer, and a frigid hall 25 °C colder. The pause menu tells the temperature where you stand, so it changes as you step in. The water in such a room freezes or thaws by the room’s temperature, so a frigid hall’s pool can be frozen on a level where every other pool is open.

Under the open sky

Outdoors and on the overworld, the temperature follows the month, the time of day, and the weather. Each month has a mean temperature, reached in the middle of the month; the days between move from one month’s mean to the next. Over a day the temperature swings around that mean: coldest around 04:00, before dawn, and warmest around 16:00. A clear sky lets the night grow cold and the afternoon warm. Clouds keep the night milder and the day cooler, and rain cools the air a little. Like the weather, the temperature is the same however you spend the time.

In the middle of each month:

What the weather does to the day’s swing (the difference between the coldest night and the warmest afternoon) and how much it cools the air:

Water freezes

Below freezing, still water grows ice, faster the colder it is. It grows quickly at first, then ever more slowly, since the ice keeps the cold from the water beneath it. Running water stays open in a mild frost, and freezes only in a hard one, and more slowly. Above freezing, ice melts 7 mm a day for every degree of warmth.

Ice does not wait for you to look. It freezes and thaws while you rest, travel, or are elsewhere, and is as it should be when you come back. A pond you first come upon in deep winter is frozen already.

From open water, at a steady temperature, still water freezes over in:

In Darkening, a pond under the open sky grows thin ice on clear nights, which the afternoon sun thins again. In Deepwinter and Frostmere it freezes thick.

Walking on ice

Ice looks like what it holds. Look mode names it:

• Thin ice: dark water shows through, with pale hairline cracks. A rat can cross it, you cannot.
• Ice: a grey-blue sheet. It holds a person; with a heavy pack, maybe not.
• Thick ice: pale and frosted all over. It holds anything that walks.

Ice too thin to see is no more than the water beneath: you wade through it, and it breaks.

What ice holds grows with the square of its thickness, as real lake ice does. 5 cm holds a person with a pack; 15 cm holds three quarters of a tonne. What counts is your weight: your own (70 kg) plus everything you carry, worn and wielded things included (see Burden).

Up to what the ice holds, it holds you. Beyond that it may give way, the more likely the more you weigh, and at twice what it holds it surely does. When it held only by luck, it creaks under your weight as a warning. A heavily laden dwarf falls in where a lightly packed elf crosses. Any ice holds someone water-borne (Water walking), however thin.

A step onto ice is a careful one and takes a little longer than on dry ground. It is no louder.

Falling in

When the ice gives way: “The ice cracks beneath you and you plunge into the freezing water!” The cold costs you a few hit points, but never your last one: for now it cannot kill you. If you are trained in Swim, you make a check as you go in: Toughness plus Swim’s points against 11. If you make it, the cold costs half as much, rounded down (“You keep your head, and the cold bites less deep.”). You are now in the water where the ice was, a hole of open water. It freezes over again in time (a few hours in a hard frost).

• Climbing out onto the ice around the hole takes a few turns: the step onto the ice plus a climb on top of it (see Turns and movement). Ice that cannot hold you breaks ahead of you as you wade on, without another plunge. Wading out onto the shore is an ordinary step.
• What lay on the ice sinks to the bottom of the hole. The water is shallow, so wade in and pick it up.
• Creatures fall through too, by the same rules, and climb out the same way.

There is no going back once the ice cracks, but you lose nothing for good: only time and a few hit points.

Heat and frost

Bursts of heat and frost change the ice at once (see Traps and spell types). A fireball melts the ice it reaches, and whoever stood on it falls in, unless they are water-borne. A frost trap freezes the water it reaches at once, into ice 10 cm thick that holds a laden person. A blast without heat would shatter thin ice, though there is no such blast yet. Someone who makes way for you, stepping onto ice you stood on, may break through it if they are heavier than you.

See also: Weather and Damage types.