On the Weather
13 October 2025
The (Nazi) philosopher Martin Heidegger had one inspiring idea in his dismissal of idle talk („Gerede“). He lamented that most conversation of (most?) people was meaningless because it limits possibility and is not authentic. The first thing most people raise in conversation is maybe the weather. It has been so hot lately. And with this talk people express their shared experience. It is wondrous. Sharing the moment in place and time with another whether good or bad is all too human. The weather does not matter for this, but it does and not only for the sake of conversation. It is everywhere grounded in nature and cannot be escaped. Heidegger’s negative view can help one appreciate even idle talk positively. But if one sees snakes in the bottom of one’s cup (unless drinking this), the shadow of the bow hung on the wall will too look like a snake.
For RPGs there is a complicated system in Dungeons & Dragons: Wilderness Survival Guide (1986, 107~118) for determining weather. It defines climates by latitude, which is logical and allows it to work in fantastic settings, but then by terrain categories (desert, forest, hills, mountains, plains, seacoast, swamp) which appear to have arisen in wargaming — not ecology. It seems to give unrealistically extreme results too often for real places (which admittedly may be more fun).
But capitulation ensued after several attempts to make a new system more accurate and easier to use.
Instead, a booklet with tables for actual places around the world covering nearly all of the Köppen-Geiger classification.
The resulting system attempts to model the alternation of Hadley cells in temperate latitudes by separating periods with and without precipitation. In order to adjudicate changes, it requires the game master to have some sense of the climate but should produce more realistic weather. In particular, the temperature range assumes that a precise number is usually not necessary, instead it being the frequency and extent of more extreme weather that is. Unfortunately, very unusual weather such as tropical cyclones fall outside of its scope: though results of extremely heavy rain together with fast winds are possible, the probability has not been confirmed.
Calculating the numbers was relatively simple upon obtaining data from a freely available climate model. But apparently climate scientists today have little understanding about the formation of clouds. Using that model, some cities known to have fog (in particular, Chongqing 重慶) resulted in little. Since fog only occurs for some hours of the day, hourly data was necessary, and this model limited this to very recent years. (The daily data are also for recent decades; it would be nice to be able to present plausible statistics for premodern cities, but a suitable model does not seem available, and existing real data for the early twentieth century are limited and seem to have many inconsistencies.) It appears this is thought to be an effect of the heat island phenomenon of contemporary cities, at least in Japan as shown by the Meteorological Agency. It would be nice to once again see the Roppongi night painted red by the glow of Tokyo Tower in fog.