I know that spells that cause exhaustion have saves but the effect from say cold etc per the rules don't mention a save.  Is there a save against it?  Also does constant exposure to the same effect require multiple saves or stacking effects?  Again the rules are not clear, it says if another effect causes exhaustion than another level is added but it doesn't say if constant exposure to the cold would require multiple saves or have a continued stacking effect.

I'm running my player through a heavy environmental challenge, they are climbing the equivelent of a Mount Everest, are lower level without magical work arounds so it's kinda important to get this one right for me and the group.

thanks,

No saves. Exhaustion is a mechanic for limiting activity, typically related to exploration. I would recommend providing ways the party can avoid it, because it can very easily turn into a death spiral (fail a check > get exhaustion > now you're worse at checks so you fail the next one > more exhaustion until you're dead).

Yeah, Exhaustion is a condition.

Some things that cause it have a save(spells, at some tables skipping a long rest will have a con save).

But if no save is listed just a trigger, then there is no save (berserker barbarians frenzy https://www.dndbeyond.com/classes/barbarian#PathoftheBerserker)

I will say, I've never played at a table that had exhaustion occur without a save

There's no general rule for being subjected to a condition. The game is full of all sorts of spells, monster abilities, class features, magic items, traps and environmental hazards that can inflict conditions and each has their own rules.

A game effect can't stack with itself and most conditions don't become worse if you're subjected to multiple instances of it. However exhaustion is the only condition that has multiple levels of severity, so effects that inflict it often do stack with themselves.

The DMG has rules for extreme environments and adventuring. Generally there will be ongoing saving throws against exhaustion if you go without food, water or sleep for too long or stay in extreme heat or cold without proper protection. But again, you have to refer to the environment rules or the rules of the adventure you're running for the details.

It's up to the DM when and what checks to make against exhaustion.

In your situation, I'd require a Con save. It's up to you the DC. Just being out with proper gear is probably a pretty easy DC, maybe even 5. Falling in an icy pond is pretty high, maybe 15. Spending a night in a blizzard on a mountain ridge without any shelter is 20 or higher.

You would usually repeat the check at some regular interval as long as they remained exposed. So if you are doing a check for camping out in the wilderness, you'd probably do it each night. But for swimming in an icy pond, it might be every round. There's no need to alter the DC unless the conditions change. Acquiring 3 levels of exhaustion will already make future saves harder, as it imposes disadvantage.

I usually decide the DC and how many times they're likely to repeat it based on how difficult I want the challenge to be, then set up the scenario to make it work. Like if I want them to feel the danger but probably suffer minimal consequences, I might make them swim 150' across an icy lake. That's five rounds of dashing with 15' swimming speed, and I'll make the DC 15, which might be around 50% for a character with decent Con and proficiency in Con saves. They're likely to get 2-3 levels of exhaustion, and there is mathematically the possibility of 5 levels, which would be death because with 0 movement speed they wouldn't get out, but there's only a 1/32 chance.

It's usually Con based, but I could imagine other options. Maybe Str save or Athletics to be able to swim a long distance. Even Int for being able to pull an all-nighter in the library or Performance for conducting a filibuster in the Senate. Acrobatics for being able to balance on the top of a pillar for hours.

In some other scenarios, the DM decides there is no save. For example, a DM who for plot reasons wants your party to go to the inn may tell you that if you stay up past midnight you get a level of exhaustion, even if you have full HP and spell slots and don't otherwise need a long rest.

Quote from scatterbraind >>

No saves. Exhaustion is a mechanic for limiting activity, typically related to exploration. I would recommend providing ways the party can avoid it, because it can very easily turn into a death spiral (fail a check > get exhaustion > now you're worse at checks so you fail the next one > more exhaustion until you're dead).

Exhaustion rolls are typically saves, which don't get a penalty until 3 levels of exhaustion.

It's been said enough. Stackable condition that goes from meh, to this sucks, to death. Many things can give you exhaustion from as written stuff (spells, environmental effects), to DM "it makes sense that this should cause exhaustion" stuff.

I've homebrewed exhaustion and use it heavily in my game. Players can cast spells up to 6 without a slot by taking exhaustion = spell level. They gain one when dropping to 0. Gain one when failing a death save, and a bit more ways.

Their con modifier acts as a buffer to exhaustion so 18 con means you don't die from exhaustion till you have 10. Con doesn't add to hp though, so it isn't the god stat that it might seem with this exhaustion system.

In long, there's lots of ways that you can work with it, as everything in D&D.

Quote from scatterbraind >>

No saves. Exhaustion is a mechanic for limiting activity, typically related to exploration. I would recommend providing ways the party can avoid it, because it can very easily turn into a death spiral (fail a check > get exhaustion > now you're worse at checks so you fail the next one > more exhaustion until you're dead).

Or, you know, they can set camp and rest.

Quote from MidnightPlat >>

Quote from scatterbraind >>

No saves. Exhaustion is a mechanic for limiting activity, typically related to exploration. I would recommend providing ways the party can avoid it, because it can very easily turn into a death spiral (fail a check > get exhaustion > now you're worse at checks so you fail the next one > more exhaustion until you're dead).

 

Or, you know, they can set camp and rest.

 Not forgetting that a Long Rest only recovers ONE level of exhaustion - so always best to rest before it gets too bad.

I saw a 1-shot campaign where the party didn't think to get horses to travel to a city under siege. So, they had to stop for the night twice to avoid exhaustion.

Riders passed them. I think the riders were added by the DM just to show the party how they need to plan a bit more.