food
a medium creature needs two pounds of food per day
cool or colder weather increases this
a creature can make food last longer by subsisting on half rations
eating half rations for a day counts as half a day without food
a creature can go without food for a number of days equal to 6 + its constitution modifier
at the end of each day beyond that limit, a creature must succeed on a dc15 constitution save or suffer one level of exhaustion
a day of eating extra rations reduces the count of days without food by one-half a day
a single berry from the goodberry spell counts as a half ration for the creature eating it
water
a medium creature needs one half gallon of water per day
increase this if the weather is warm or warmer
a character who drinks only half that much water must succeed on a dc 15 constitution saving throw or suffer one level of exhaustion at the end of the day
a character with access to even less water must succeed on a DC 15 Constitution saving throw or suffer one level of exhaustion once every twelve hours
precipitation
stage one: clear
stage two: clear plus light rain, freezing rain, light snow
stage three: partly cloudy
stage three: partly cloudy plus rain, hailstorm, or snow
stage four: overcast
stage five: overcast plus torrential rain, sever hailstorm, or blizzard
clear the unobstructed outdoor light is sunlight
light rain extinguishes small flames and gets everything wet
freezing rain extinguishes small flames, gets everything wet, and may cause icy terrain
light snow extinguishes small flames
partly cloudy the outdoor light is bright light
rain imposes disadvantage on wisdom (perception) checks that rely on hearing and extinguishes all but magical open flames
hailstorms cause all creatures near it to have disadvantage on wisdom (perception) checks that rely on hearing, extinguishes all but the largest open flames, and attacks each creature in the open with a +0 bonus for 1d6 bludgeoning damage
snow causes everything within the area of snow to be lightly obscured and extinguishes all but magical open flames
overcast the outdoor light is low light
torrential rain causes everything within its area to be lightly obscured, imposes disadvantage on nearby wisdom (perception) checks that rely on hearing and extinguishes all but magical open flames
heavy hailstorms cause everything within the area of a heavy hailstorm to be lightly obscured, all creatures near it have disadvantage on wisdom (perception) checks that rely on hearing, extinguishes all but magical open flames, and attacks each creature in the open with a +0 bonus and advantage for 1d8 bludgeoning damage