OED Wilderness Rules Draft: Weather Events

The fourth and final part of a draft of modified wilderness adventuring rules for OED-style games. Something like this was playtested at Helgacon this year. The principal feature it that it exchanges the daily Lost die for a simple Weather mechanic. Whereas in the past I've struggled in Sisyphean style with super-complicated weather rules (e.g.: Dragon #68 "Weather in the World of Greyhawk", AD&D Wilderness Survival Guide), this simple d6 roll is making me perfectly happy in play now. Thoughts?

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Weather Events

In wilderness adventures we replace the daily Lost die roll (see Vol-3, p. 18) for a Weather roll. Thus two dice a rolled each day: a red die (for Encounters) and a blue die (for Weather). On a roll of 5-6 some weather Event occurs; consult the table to the right. The default situation assumes a temperate environment in the summer, with a base daily temperature of Warm (clo 0).

Heat Wave: Daily temperature is Hot (clo –1). No travel or work can occur without magical protection.

Light Rain: Travel may be attempted normally, but there is a 2-in-6 chance of becoming lost (mostly travel in circles, end move 1 hex in random direction).

Heavy Rain: Travel is impossible (except possibly for large creatures like giants, ents, balrogs, etc.)

Thunderstorm: Travel is impossible, and parties not in shelter have a 1% chance of a random character being struck for 6d6 lightning damage (save for half).

Travel prohibitions generally mean that no encounters can occur (except as indicated). We assume that no long-range movement occurs in the winter season (due to snow, cold weather, muddy roads, blocked mountain passes, etc.), including sea travel. The DM is encouraged to create Event tables for other climactic zone as desired.

Notes and References

• The specific frequencies of events above were modeled on northern Europe; specifically the Paris Le Bourget airport in June to August. We downloaded daily historical weather data for these months 2001-2009 and computed statistics as above. Paris was chosen as central to battles in the Hundred Years War. Technically, a d8 Event die would be more realistic (1-in-8 heat wave, 2-in-8 thunderstorm), but the d6 was used above for simplicity in play. https://www.wunderground.com/history/
• Frequency of rainy days may be 25-50% in Atlantic region, northern Europe. Heavy rain (> 10mm per day) occurs in eastern United States about 15% of days (1 in 6), Europe somewhat less. Rainy days evidence clustering (suggests roll for multi-day duration, or increased chance next day?). http://www.cgd.ucar.edu/cas/adai/papers/Sun_etal_JC06.pdf
• This short table of middle ages battles shows battles occurring from March to October, with the largest cluster from June to August, which we used as the assumed “adventuring season”: http://www.medieval-life-and-times.info/medieval-history/medieval-battles.htm
• People walk in circles when lost (contrast this with the rule in Outdoor Survival/OD&D in which being lost causes travel in a maximal straight-line path, being unable to turn or stop):

   http://news.nationalgeographic.com/news/2009/08/090820-walk-in-circles-video-ap.html, http://www.livescience.com/33431-why-humans-walk-circles.html
• No winter sea travel as given in Unger, Richard W., The Ship in the Medieval Economy 600-1600. (p. 128, 131; but compare to later era on p. 175). If winter sea travel permitted, then weather should also be modified in that season.
• For a translation of a year-long medieval weather record, possibly by Roger Bacon, see the link below (cites C. Long, “The Oldest European Weather Diary?”, Weather, Vol.29:6 (1974) pages 233-237): http://www.medievalists.net/2015/09/a-medieval-weather-report/
• For more exotic weather options reported in medieval times (such as cooked wheat, barley, beans, fruit, fish, snakes, stones, ash, rocks, people, slabs of ice, and blood), see Paul Edward Dutton, “Observations on Early Medieval Weather in General, Bloody Rain in Particular”, The Long Morning of Medieval Europe: New Directions in Early Medieval Studies (Chapter 9) (currently available on Google Books search).