What counts as a sufficient heat source to survive Amber Temple?

Question

In the Curse of Strahd adventure, the sidebar about Amber Temple's temperature (p. 181) says:

Extreme Cold

The Amber Temple is a cold, dark place carved out of the snowy slope of Mount Ghakis. The temperature throughout the complex is -10 degrees Fahrenheit (-23 degrees Celsius). Characters who don't have heat sources, cold weather gear, or magic to protect them are subject to the effects of extreme cold, as described in the "Weather" section in chapter 5, "Adventure Environments," of the Dungeon Master's Guide. If Kasimir Velikov (see chapter 5, area N9a) is with the party, his ring of warmth protects him from the effects of the extreme cold.

It specifically mentions "heat sources", and I was wondering what counts as a heat source for the purposes of not succumbing to the cold of Amber Temple.

Is a torch good enough? Or are we talking more like a campfire (say, the sort that someone might make during a long rest)? I imagine Curse of Strahd itself doesn't expand much more on this, but there might be some generic rules in the DMG or similar that I haven't managed to find with regards to temperature?

I ask because there will be at least one party member who won't have any (relevant) magic items, cold resistance or cold weather gear by the time they enter Amber Temple, and I'd like to know what counts as a heat source so I (as the DM) know when to ask for or waive the need for saving throws vs. exhaustion.

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For reference, the "Extreme Cold" (Dungeon Master's Guide, p. 110) section:

Whenever the temperature is at or below 0 degrees Fahrenheit, a creature exposed to the cold must succeed on a DC 10 Constitution saving throw at the end of each hour or gain one level of exhaustion. Creatures with resistance or immunity to cold damage automatically succeed on the saving throw, as do creatures wearing cold weather gear (thick coats, gloves, and the like) and creatures naturally adapted to cold climates.

Answer 1

“Extreme cold” is extremely cold

The temperature in the Amber Temple is what you get in North America, Scandinavia, or Siberia a few times a year.

There are no cities anywhere in the world where the average winter nighttime temperature is that cold although those temperatures are reached on occasion. So you need to be thinking of the coldest places on Earth on some of the coldest nights of the year.

You are going to need more than a torch. Within the abstractions of D&D a torch is more a source of light than of heat. You need to be thinking in terms of a decent sized fire for a considerable period.

However, by the time the characters get there they should have magical options to resist the cold or create cold weather clothing.

Of course, the people in the first room have cold weather clothes or else they’d be dead. My players just killed them and took their stuff.

Answer 2

The rules don't say

This is the sort of situation where you, as the DM, are expected to make up a ruling. We can tell you what sort of ruling we would make at our tables, but we can't give you a Definitive Answer.

At my table, I would rule that a torch (or any larger portable fire) is not enough of a heat source to stay warm. If a character tried to stay warm using a torch, some parts of that character would be uncomfortably hot or burning, while other parts of a character would still be too cold. To stay warm, a character would need to have a decent-sized fire which could warm up an area.

(Note that there are zero IRL incidents of people going out in cold weather and holding a torch to warm them up. The fact that nobody does it in real life should be a strong clue that it doesn't work.)

If my group was in a cold area such as this, I would expect them to (1) have winter clothing such as a heavy winter coat, (2) leave the area and go find a town and buy a heavy winter coat, (3) run through the area quickly and leave within an hour, or (4) make use of magic, such as periodically ritual-casting leomund's tiny hut to warm up.

Answer 3

Heat sources

Confining ourselves to just the items of adventuring gear listed in the PHB p. 150, the following might be considered heat sources:

Alchemist's Fire

Candle

Lamp

Lantern, bullseye

Lantern, hooded

Oil (flask)

Torch

Of these, alchemist's fire and an oil flask (by itself) will burn quickly (perhaps explosively) and then go out.

The others will burn longer, but would not produce enough heat to warm even a small room unless they were present in great quantities.

However, another item on the list is a two-person tent. This is a small enough enclosed space that it could be heated by some of these heat sources. (Note: Do not try this in real life)

A torch, if it did not immediately catch the tent on fire, would soon fill it with smoke.

However, I would rule that several candles, a lamp (with oil), or either lantern (with oil) would count as enough of a heat source to heat a two-person tent in extreme cold to the extent that cold weather gear was not necessary to bypass the exhaustion-inducing Constitution save. I would likely also rule that some sort of Dexterity save was needed for the occupants of the tent to not upset the heat source and catch the tent on fire, with a high DC for the lamp, a middle DC for the candles, and a low DC for the lantern.

If you allow the purchase of gear outside of what is on the list in the PHB, I would rule that a brass or iron camp stove and coal (mineral coal, not charcoal) could keep a tent or a very small room (10' x 15' or smaller) warm enough to go without cold weather gear.