Weather and Book of War 2E Units

You may have seen on the Saturday night Book of War wargame livestream that Isabelle & I have started playing with monster-types and variant weather rules (which is important for balancing light-sensitive monsters, missile troops, etc.) I've been grappling with balanced, easy-to-use weather rules for eons, trying to get something that works efficiently across (1) the wargame table, (2) D&D wilderness exploration, and (3) the 6th-level control weather spell.

Here's the current, very simple idea: just roll 1d6 each day.
  1. Clear
  2. Scattered
  3. Broken
  4. Overcast
  5. Light Rain
  6. Heavy Rain

On results on 1-2 you have "full daylight or bright light" sufficient to trigger goblin and orc weakness in the daytime. Results 3-4 have no special effect. The 5, Light Rain result has no effect in large-scale operations (wargame or long-distance travel), but applies −2 to missiles in the man-to-man context. The 6, Heavy Rain result gives 1/2 movement for all (doubled for mounted troops), −4 to missiles (converts to −1 in wargame scale), and all mounts and pikes lose special bonuses.

These might seem rather gentle for top-level weather penalties. In particular I've snipped out the "Stormy" category that I had in Book of War 1E. But this closely mirrors the possibilities in the Chainmail system, Dragon #68 (official Greyhawk weather), Battlesystem, etc. The distribution of rainy days is a pretty good match for historical data in Europe and the U.S. in the summer. In wilderness adventure situations, you basically just need to roll an extra 1d6 each day and look for the "6". And the effects seem basically game-balanced, and something for which we don't need to gimp control weather too badly (i.e., okay for it access any level on demand).

As an aside, I did some assessments of the unit matchups in the different weather conditions: the upshot is the a player opting to take goblins/orcs is taking a big gamble. In the 1-2 sunny state, they're pretty close to useless trash. In the 3-5 cloudy state, they're at the top of the heap; especially the archers and wolves. In the 6 rainy state, then it's the close-combat infantry types that have a big advantage; and meanwhile it's any mounted type that gets put in the effective garbage bin (including wolves). We'll see in further tests if that makes for acceptably interesting gameplay.

Here's the current list of all units being tested. Comments welcome!

Book of War 2E Units List - 200726


  1. What do you think of using this system, but where the die controls the direction of the weather change. E.g. 1-2 things move one step better, 3-4 no change, 5-6 things move one step worse.

    This will give more stretches of consistent weather, which will allow for better strategic planning.

    1. It's probably too consistent; precipitation and cloud cover are actually quite a random walk. At most, I'd say you could use a larger die with a "same as yesterday" entry, if you wanted finer distributions.

      Instead, I'd suggest a lower level spell (and/or magic item and/or specialist NPC) that lets you predict the weather for a few days in advance.

    2. Yeah, I see why you're saying that, but I agree with Joshua that weather varies a bit more quickly than that. E.g., I've wrestled with a "thunderstorm" condition a lot; in the real-world, t-storms almost always pass inside of 30 minutes, so using that for a daily descriptor (one that affects movement all day) is erroneous.

      Gygax's original weather in Chainmail bumped up or down on 2-minute intervals (maybe too fast). A lot of weather system have, e.g., roll a die for how many days this system lasts, but personally I really don't want the state/record-keeping.

  2. Is the assumption that you've collapsed together penalties for heavy rain with penalties for muddy terrain? The movement penalties and extra penalties for pikes and cavalry seem to suggest so, but I can think of plenty of times where a heavy rain shower is short-lived enough to not create too much mud, or other times when everything is muddy due to two or three straight days of light rain without rather than any single downpour - and especially in those cases, will often still be muddy the next day after the rain has stopped.

    I guess the crux of my comment is that I feel like there should be a possibility of mud penalties separate from weather penalties, rather than assuming heavy rain = mud and all other weather = no mud.

    1. Good catch, yes. Here's a few threads that fed that: (a) It synchs with Chainmail weather, where that's precisely the distinction between Light Rain and Hard Rain (footnote: "Three turns of hard rain brings mud, reducing movement by 1/2".

      (b) This also gets used in RPG overland travel, where it represents precipitation over the course of a whole day. E.g.: "Heavy rain" might be a day with some scattered showers, clearing, hard rain, thunderstorm, over 24 hrs.

      I considered tracking multiple dimensions of weather (many systems do) like temperature, wind, precipitation, but decided against it as too complex. I really need just a single die-roll (added to the OD&D encounter & lost dice) that I can read & interpret instantly on sight each day-turn of movement. So: Very broad categories.