Weather
The weather is worked out every game hour over the whole disc, in cells 2 km across. It comes only from the world’s seed, the land and the sun, so the same world at the same hour always has the same weather, and co-op players share it.
What makes it
Section titled “What makes it”Each cell has a temperature, pressure, wind, humidity, cloud, rain or snow, storms and fog. Land warms by day and in summer, and high ground is colder. Wind blows down the pressure slope, pours off the rim and drains down valleys at night. Fog lies in still damp hollows and by water.
Lows and highs travel across the disc, a new one every day or two. Lows bring cloud and rain, with a cold front and colder air behind it. Highs clear the sky.
Seasons
Section titled “Seasons”| Season | Weather |
|---|---|
| Spring | Cool by the sea |
| Summer | Settled and warm, with afternoon thunderstorms over hot land |
| Autumn | Mild by the sea |
| Winter | Grey and stormy, with snow, frost and deeper lows |
The warmest and coldest days come a few days after midsummer and midwinter, later by the sea.
Clouds lie on a layer 3 km up and drift with the wind. Where the cover is thickest a cloud stands up through the layer, and on stormy days a tower. Under a thick deck the light turns flat and grey, and storms flash with lightning. Now and then a rain cloud on the sunny side shows a rainbow, and seen from above a cloud’s top may show a glory.
Snow lies where it falls, building up in a cold spell and melting in warmth, rain and sun. Above the snowline it lies all year. The snowline sits about 850 m up in summer and about 300 m in winter in temperate country. Deep snow slows armies by up to half, and at 150 cm it shuts the high passes until spring.
Floods and surges
Section titled “Floods and surges”Rivers rise after heavy rain and with the snow melt, up to 2 m, and fall again over a day or two. A ford closes from 0.8 m and a stream away from a crossing from 1 m, so armies must find a bridge.
A deep low with an onshore gale lifts the sea over low land behind the shore, furthest at high tide. It never reaches a settlement. Flooded land cannot be marched over.
What it does
Section titled “What it does”| Weather | Effect |
|---|---|
| Rain, snow, mud, storms | Armies on the map slow, down to 0.35 of their pace |
| Heavy rain | Sight falls to 0.6 |
| Fog, snowstorm | Sight falls to 0.3 |
| Mud, deep snow | Men and horses slow in battle |
| Rain, gusts | Arrows fall short and miss |
| Smoke | Blocks a line of sight |
| Rain or snow on a camp | Soaks it through at 4 mm an hour; men rest half as well |
| Rain over the growing season | Sets each village’s harvest |
Wet ground darkens and soft ground on the flat turns to mud in patches. Hard frost freezes it so it neither soaks nor turns to mud.