Weather in Games
I am currently running a Fantasy rpg using the simple free d100 rules Hack 100 and Rob Conley's setting of The Majestic Realms using the expanded Blackmarsh setting.
I wanted the weather to play a big part in the Campaign as the players are active in the Northern Reaches particularly around the Great Glacier. So first job was to find a comparable place here on Earth and I settled on Finland with the city of Tampere as reference point.
Using Weatherspark.com I mapped out the relevant historical data for each month:
- Temperature, extreme highs and lows, and average highs and lows
- cloud cover my month as a percentage
- precipitation by month (rain, sleet, snow)
- hours of daylight, together with the sunrise times per month
- average wind speed per month and direction percentage
The only thing I didn't need was Moon and its phases as I had written a custom calendar with a uniquely named months , each of 30 days, and each moon cycle lasted 30 days.
As I was running this in Foundry I made random tables for each month covering the data I had gathered. The main table shows the main details and links to other table where appropriate, it would also only roll for rain/snow if the skies were cloudy and not clear. So for January the table is:
January Weather
| Roll | Result |
|---|---|
| 1-2 | Clear |
| 1-100 | Temp: -30+6d6 C |
| 1-100 | Sunrise: 09:00, Sunset: 15:00 |
| 1-100 | Roll on Wind table |
| 3-5 | Mostly Clear |
| 6-18 | Partially Cloudy |
| 19-46 | Mostly Cloudy |
| 19-100 | Roll on Jan Precipitation table |
| 47-100 | Overcast |
Wind Table
| Roll | Result |
|---|---|
| 1-10 | High Wind |
| 1-66 | Roll Wind Direction Table |
| 11-37 | Light Wind |
| 37-66 | Slight Breeze |
| 67 - 100 | Calm |
Wind Direction Table
| Roll | Direction |
|---|---|
| 1-20 | From the North |
| 21-40 | From the East |
| 41-75 | From the South |
| 76 - 100 | From the West |
January Precipitation Table
| Roll | Result |
|---|---|
| 1-11 | Heavy Snow |
| 12-17 | Mixed, Sleet |
| 18-22 | Rain |
| 23-100 | Dry |
Result
Example rolls:
- Roll: Overcast, -8 C, Dry, Sunrise: 09:00, Sunset: 15:00, Calm
- Roll: Mostly Clear, -12 C, Sunrise: 09:00, Sunset: 15:00, Moderate Wind, From the West
Conclusion
I am happy with the result, the rolls I am getting are very similar to the Tampere weather. The lengthiest part was looking up the historical data and just tweaking the monthly tables for the weather