On Weather and Travel in Wilderness Adventure

Currently, I’m in the process of writing and designing a setting for use is Old School Essentials (or your OSR system of choice really). As I work through some of the optional mechanics, I plan to publish them here for feedback and for you to use, or modify, as you see fit. In this post, I share a draft for my weather procedures for Dungeons and Dragons.

Weather Procedure for your OSR or D&D Adventure

To add to the adventure atmosphere (ba-dum-tiss!) and help bring the campaign setting and overland travel to life for your players, the weather should be somewhat unpredictable for the Player Characters. However, in some instances, the weather forecast can, and should, be more accurately predictable based on observation and common knowledge. If you are an adventurer or a merchant who travels overland, say, from one town to the next, your experience would likely inform you of weather patterns to be aware of. You might hunker down if you know a storm is brewing instead of risking travel. Or if you might try and beat the storm with a forced march. 

The idea of the weather table for wilderness adventure, from a DM perspective, is to give the Players something to react to. It is something that may complicate their plans if they don’t take action. But, if the weather were determined at the start of every day of travel, then that doesn’t leave much for the players to make meaningful choices around—there’s not much of a choice if it’s raining now.  However, if a storm is coming within the next couple of days, now the party can decide whether to head back to town with their treasure or press onward.  

Rolling for Weather

If needed, roll on the weather table at the start of the day then adjudicate the results.

d20	Weather
1-10	Normal for the season.
11-16	Weather Change: Hotter (1-10) or Colder (11-20)*
17-19	Precipitation (normal for the season) (2d6 hours)
20	Sudden Storm (2d4 hours)
	*Hotter = storm is coming, Colder=less severe precipitation is ahead

Normal for the Season

The weather is typical for whichever season the party is currently experiencing.  

Weather Change 

If there is a change in the weather, roll again to determine if it is a cold front(warmer) or a warm front(cooler)—either result will begin a timer of 1d4-1* days. After which, the weather change will result in either mild precipitation or a storm depending on the nature of the change (Hotter = storm is coming, Colder=less severe precipitation is ahead). The storm or precipitation that follows a weather change will be more powerful and last longer than an onset result. For either, double the duration roll.

*On a result of 0, the weather event is bound to transpire today sometime.

Precipitation

A gentle rain or snow (depending on the season) falls. 

• Travel speed is slowed by 25%. 
• Chance of losing direction is increased by 1-in-6.

Storm

Thunder cracks and rumbles, and lightning flashes as heavy rain pours down. Strong winds blow.

-or-

A heavy snow and blustery wind whips at you, chilling your bones. (if adventuring in the winter)

• Travel speed is slowed by 50%.
• Chance of losing direction is increased by 2-in-6

Note

This system is a work in progress. I will update this post if any tweaks are made in the future.