Grisly Eye Games

Random Weather

Weather Illustration

Copyright free woodcut from the History of the Nordic Peoples by Olaus Magnus.

These rules for weather are for gritty campaigns where travel is difficult and resources like rations and water are valuable. This is an excerpt from my forthcoming campaign, Black Griffin.

Depending on the season, pick a weather die as per the table below. For example, in Spring you would roll a d6.

Season Die
Spring d6
Summer d8
Autumn d6
Winter d4

Each day of travel make a weather check to determine the weather. Roll the weather die and consult the table below:

Weather Check Weather Condition
0 or less Very Cold. Make a DC 16 Constitution saving throw or take 1d10 cold damage per day exposed. Roll with advantage if you’re wearing traveller’s clothes. There is a 1 in 4 chance there is a blizzard, in which case all Perception checks have disadvantage.
1-2 Cold. Make a DC 13 Constitution saving throw or take 1d6 cold damage per day exposed. Roll with advantage if you’re wearing traveller’s clothes. There is a 1 in 4 chance there is a storm, in which case all Perception checks have disadvantage.
3-4 Snowing/Raining/Mist. Due to low visibility all Perception checks have disadvantage.
5-6 Mild. No effect.
7-8 Hot. Make a DC 13 Constitution per day exposed. If you fail your saving throw take 1 level of exhaustion. Roll with advantage if you’re wearing traveller’s clothes. Make the saving throw with disadvantage if you’re wearing heavy armour. You can ignore this condition if you double your water rations.
9+ Very Hot. Make a DC 16 Constitution per day exposed. If you fail your saving throw take 2 levels of exhaustion. Roll with advantage if you’re wearing traveller’s clothes. Make the saving throw with disadvantage if you’re wearing heavy armour. You can ignore this condition if you triple your water rations. There is a 1 in 4 chance there is a storm, in which case all Perception checks have disadvantage.

Adjust the roll by the region’s climate modifier (+4 to -4):

Climate Modifier
Polar -4
Cold -4
Temperate 0
Warm +2
Tropical +3
Arid +4

I was aiming to make these rules as simple and flexible as possible. I really like the fact they only use one roll. But I do worry they're a bit swingy: a temperate summer's day could be cold or hot from one day to the next. For anyone who has lived in the UK this may not seem strange, but not sure it's entirely realistic. Maybe the key is to make weather checks less frequent, perhaps once every other day. Or switch the summer weather die from a d8 to a d6+2.