the tundra gives you resistance to cold damage and lets you not suffer the effects of extreme cold, as it is described in the dungeon master's guide, and the desert gives you resistance to fire and lets you ignore extreme heat in the same way. Only problem is that according to the dungeon masters guide creatures who are immune to cold damage already do not suffer the effects of extreme cold and creatures immune to fire damage already do not suffer the effects of extreme heat, so why would they even mention that. And what is more even without those resistances you can still overcome both those environmental hazards via normal common sense protective measures such as just staying properly hydrated and wearing warm clothes, so what is even the point of being immune to these things in the first place?

It's specifying for simplicity and thematic purposes. It's not necessary for them to say it, but doing so adds flavour.

You still get the resistances plus other benefit mentioned.

I don't understand your issue.

Quote from Cyb3rM1nd >>

It's specifying for simplicity and thematic purposes. It's not necessary for them to say it, but doing so adds flavour.

You still get the resistances plus other benefit mentioned.

I don't understand your issue.

 And it also implies the player doesn't need the DMG to learn about that information.

Additional note: "Immunity" is not "Resistance".  Plenty of PCs have resistance to fire or cold damage, but do not have any especial protections from extreme environments.  Tiffles, for example, are almost universally resistant to fire, but are just as helpless in the face of desert heat and weather conditions as any regular-ass manfolk.

Quote from Yurei1453 >>

Additional note: "Immunity" is not "Resistance".  Plenty of PCs have resistance to fire or cold damage, but do not have any especial protections from extreme environments.  Tiffles, for example, are almost universally resistant to fire, but are just as helpless in the face of desert heat and weather conditions as any regular-ass manfolk.

 
From DMG - Chapter 5 - Adventure Environments - Wilderness Survival - Weather: (emphasis mine)

Extreme Cold

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.

Extreme Heat

When the temperature is at or above 100 degrees Fahrenheit, a creature exposed to the heat and without access to drinkable water must succeed on a Constitution saving throw at the end of each hour or gain one level of exhaustion. The DC is 5 for the first hour and increases by 1 for each additional hour. Creatures wearing medium or heavy armor, or who are clad in heavy clothing, have disadvantage on the saving throw. Creatures with resistance or immunity to fire damage automatically succeed on the saving throw, as do creatures naturally adapted to hot climates.

Noted.  My mistake.  Does seem a little odd, but could be reasoned either way.  Thanks for the clarification.

I love it how this is one instance in which WotC actually explains something very clearly and it still confuses people.

Well, in my case I avoid the DMG like the plague.  Unless there's a specific table or something I need from it, that book can stay in the hazmat bin where it belongs and can't contaminate anything else.  The 5e PHB is pretty good.  The DMG is a radioactive disaster.  Sometimes that means I miss details I shouldn't.  Ah well.

Quote from Yurei1453 >>

Well, in my case I avoid the DMG like the plague.  Unless there's a specific table or something I need from it, that book can stay in the hazmat bin where it belongs and can't contaminate anything else.  The 5e PHB is pretty good.  The DMG is a radioactive disaster.  Sometimes that means I miss details I shouldn't.  Ah well.

 That’s going a bit far. The DMG is good for three things:

1. Magic Items.
2. Looking up stuff like this.
3. And helping people who have no idea how to DM.

Quote from Yurei1453 >>

Noted.  My mistake.  Does seem a little odd, but could be reasoned either way.  Thanks for the clarification.

 No, what was odd was back in 2nd edition when fire and magical fire were different damage types and your resistance to each wasn't automatically the same.  So you could have someone with immunity to magical fire but not fire, meaning that he could tank all the Fireball spells in the world but still burn his mouth eating soup that was too hot.

Quote from 6thLyranGuard >>

Quote from Yurei1453 >>

Noted.  My mistake.  Does seem a little odd, but could be reasoned either way.  Thanks for the clarification.

 No, what was odd was back in 2nd edition when fire and magical fire were different damage types and your resistance to each wasn't automatically the same.  So you could have someone with immunity to magical fire but not fire, meaning that he could tank all the Fireball spells in the world but still burn his mouth eating soup that was too hot.

 i guess magical fire burns the soul while regular fire burns the body

There was never any logic to it.  Especially since other elemental damage types, like cold, weren't given such a distinction.