Sandstorm says the following on fire resistance, in the context of environmental danger:

A character with a spell or effect granting resistance to fire applies this resistance to both lethal and nonlethal damage from hot temperatures.

Since someone with a ring of minor fire resistance has resistance to fire 10, and no temperature band is able to deal more than 10 nonlethal damage, and nonlethal damage from heat exposure is what causes heatstroke, that person is immune to heatstroke and the corresponding fatigue as long as they keep their ring on. (Maybe the exact timing of things isn't specified for if they take the ring off, but I don't particularly care about that)

That's all well and good, but then the very next section in Sandstorm covers dehydration.

... the creature must make a successful Constitution check each hour (DC 10, +1 for each previous check) or take 1d6 points of nonlethal damage. In particularly hot environments (those above 90° F), the time a creature can go without water before making Constitution checks is reduced

Nothing in there makes any mention of fire resistance having any impact on the amount of time before dehydration checks start to take place. It also doesn't say that the damage is "from hot temperatures", which is what the first quote said fire resistance reduces.

Does this mean that a half-red dragon half-fiend, with both immunity to fire and resistance to fire 10, gets dehydrated by hot temperatures in exactly the same way as Joe Average the human?

Same deal with sunburn:

If a character is caught out in the sun and completely unprotected ... the character is mildly sunburned and takes 1 point of nonlethal damage. After 3 hours more exposure, the character develops severe sunburn and immediately takes 2d6 points of nonlethal damage and a -2 penalty on Fortitude saves to avoid damage or fatigue from heat dangers until the nonlethal damage is healed.

The damage here isn't "from hot temperatures" either. And even if it were, the penalty on Fortitude saves isn't even "damage". So is this to say that our scaley fiend once again suffers sunburn just as quickly and just as severely as Mr. Human, or at least some reduced form of severe sunburn, despite being able to withstand the temperatures of the literal surface of the sun?

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    \$\begingroup\$ To be clear: Is the question about that half-red dragon half-fiend creature under these rules or is the question How does fire resistance (and, by extension, fire immunity) interact with the expanded rules from Sandstorm covering the dangers of extreme heat exposure? \$\endgroup\$ May 5, 2020 at 14:03
  • \$\begingroup\$ The latter--the dragon/fiend was just an extreme example of a creature that has both resistance and immunity (though I'm realizing now, not a particularly "clean" example, whoops), but if resistance and immunity behave differently, then those particular interactions are still of interest to me. \$\endgroup\$
    – 47948201
    May 5, 2020 at 23:19

1 Answer 1


Your half dragon-half fiend is likely immune to getting sunburned, and is definitely immune to becoming dehydrated.

First, the dehydration: Half-fiends are Outsiders, and as such, they do not require food, drink, or sleep to sustain themselves. If you don't need water to sustain yourself, then not having water is unlikely to affect you in basically any way.

Secondly, as a half-dragon, they are (mostly) covered in scales. You see, a reptiles' scales protect its epidermis from the harmful UV light emitted by the sun, so that alone prevents it from getting sunburned. A creature covered in scales is more likely to die of overheating before it would get even a mild sunburn, and with an immunity to fire, our half-dragon half-fiend is unlikely to have that problem either.

Disclaimer: this bit is opinion

As for other creatures with strong fire resistance/immunity, it wouldn't really make sense for them to become dehydrated more quickly due to high temps, since they resist such temp increases. Sunburns, on the other hand, would be dependent on the strength of the creatures resistance. If a creature has any amount of fire resistance, I would say they're immune to the first stage of sunburn, but they would need a resistance value of 12+ (since it can be as much as 12 points of damage) to be guaranteed immune to the second stage, or have some other means of protection, such as natural protection like scales, or protective clothing/magic.


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