Saturday, 4 February 2023

Hex Crawl 23 #35: Flat Valley with Weather System and Spring Weather Report

Three hexes northwest of Alakran.

In this dull stretch of land between the low, eroded ridges that mark the beginning of the Dhuga range, let's talk about the weather.

I realize I never updated my old post about weather dice to discuss the dice system I have ended up using in actual play for many years. It relies on normal d6, not the Chessex weather d8, and has been fairly successful across a few campaigns.

Weather for the day (or a 12 hour or 6 hour period) is determined by a roll of 3d6, which are looked at separately for a combined weather picture. The overall impression comes form the following icon table, which somewhat corresponds to the standard arrangement of pips on the die:

Temperature is determined by the preponderance of 1's to 5's. The two cancel each other out; each 1 not matched by a 5 correspond to warmer temperatures of +10F/5C, and each 5 not matched by a 1 to colder temperatures of -10F/5C, compared to the average for the climate and season. The average temperature in Spring in the region is 75F/22C by day and 60F/15C by night.

Wind is determined by the preponderance of 3's compared to 1's. The typical climate norm, observed in the region, is for light breeze (1-2 on the Beaufort scale); if 3's outnumber 1's by 1 it means light wind (3-4), by 2 it means strong wind (5-6), and three 3's means a dangerous wind (7+). More 1's than 3's means dead calm. The Scarp means that winds from the east in East Wahattu, and from the west in west Dulsharna, are not often seen. Dangerous winds from the south will be sandstorms in the second and third months of spring.

Clouds and precipitation depend on climate, which determines how much 4 and 6 results are cancelled out in general or by other die results. A 6 result always comes with clouds.

The first month of Spring, called Nisannu throughout the region, comes after the rainy winter and is a "very dry" climate. One 6 is automatically cancelled, and 1-2 cancels 4-6. This means that light rain requires two 6'es with no 1-2's to be rolled, and moderate rain is only had once every other season (3 6's, 1/216 days).

The other two months, Iyarru and Simannu, are "arid." In the daytime, one 4 and two 6's are automatically cancelled out, and 1-2 cancels 4. This means cloud cover is rare and light rain very rare. In the night, clouds and rain occur as in Nisannu.

In the war between sun and clouds, throughout Spring, 1 (no clouds) will always win over 2 (partly cloudy).

Continuing weather: If you want to simulate consistent weather day to day, roll 3 dice in order and one extra,  and if the extra rolls a number you saw the previous day, swap it in for the first number rolled you did not see the previous day.

You can also do this for 12 hour (3+2 dice) or 6 hour (3+3 dice) periods.

Example: Weather covering the days 4 through 6 Nisannu is rolled.

4 Nisannu: 5-1-1 means it is hot and cloudless (one more 1 than 5); 27C by day and 20C by night.

5 Nisannu: 4-5-4 + 5. We drop the 4 and substitute the 5, making 5-5-4. Ironically this means a sudden change to cold, cloudy weather, only 12C by day and overcast!

6 Nisannu: 5-6-5 + 6. The added 6 does not match the previous day so it is dropped. The cold weather continues, so does the cloud cover (a cancelled 6 still means some cloud), and it seems it is trying to rain -- but does not succeed because one 6 is cancelled.

Daily weather gives texture to travel and activities outdoors, and sometimes can throw challenges of extreme heat, wind, and precipitation at the players -- which will be detailed more in a later post.


  1. I always struggle with weather, and I like this system. Though I am also thinking about the hex flower process as that makes weather dependent on previous weather so not quite as random.

  2. Yep, it really would be interesting to see how this matches up day to day with how consistent weather is in the real world. But for my purposes it has turned out OK, as the times when players need to notice the weather can be spread out.