TEMPERATURE

A creature that spends enough time in extreme weather conditions must succeed on a Constitution saving throw against the appropriate DC or suffer one level of exhaustion.

WEATHER HAZARDS

Rules for weather hazards.

BLIZZARD

A blizzard's howling wind limits hearing to a range of 100 feet and imposes disadvantage on ranged attack rolls. It also imposes disadvantage on Wisdom (Perception) checks that rely on hearing. The wind extinguishes open flames, disperses fog, erases tracks in the snow, and makes flying by nonmagical means nearly impossible. A creature falls at the end of its turn if it is flying by nonmagical means and can't hover.

Visibility in a blizzard is reduced to 30 feet. Creatures without goggles or other eye protection have disadvantage on Wisdom (Perception) checks that rely on sight due to blowing snow.

Any creature that is concentrating on a spell in a blizzard must succeed on a DC 10 Constitution saving throw at the end of its turn or lose its concentration on the spell unless the creature is sheltered against the elements (for example, in an igloo).

Veering Off Course. It's easy to veer off course while traveling through a blizzard, and it's also easy for party members to become separated from one another, which is why the wisest course of action is to stay put and wait for the blizzard to pass.

If the characters travel during a blizzard, have the players designate one party member as the navigator. At the end of each hour of travel through the blizzard, the DM makes a DC 15 Wisdom (Survival) check on behalf of the navigator. On a successful check, the party stays on course. On a failed check, the party wanders off course, putting its members no closer to their destination than they were at the start of that hour. If the check fails by 5 or more and the party members aren't tied together, one randomly determined party member becomes lost in the blizzard and separated from the others. If the group tries to reunite with its missing member, have the party members (including the missing one) make a DC 15 Wisdom (Survival) group check at the end of each hour. If this group check succeeds, the missing party member is found, but no progress is made toward reaching the group's intended destination that hour. The group check can be repeated after each hour spent searching for the missing party member.

COLD

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 clothing (thick coats, gloves, and the like) and creatures naturally adapted to cold climates, such as reindeer and snowy owlbears

WIND

A strong wind imposes disadvantage on ranged weapon attack rolls and Wisdom (Perception) checks that rely on hearing. A strong wind also extinguishes open flames, disperses fog, and makes flying by nonmagical means nearly impossible. A flying creature in a strong wind must land at the end of its turn or fall.

A strong wind in a desert can create a sandstorm that imposes disadvantage on Wisdom (Perception) checks that rely on sight.