1. Use simple editor for it, so:
2. Load scenario. Don't run it, but use simple editor option when scenario is ready to play.
3. 7th upper button is called TABLES. Use this one.
4. Historical weather is 1, random is 2, bad is 3. So you probably want to use number 3. But..
5. In TABLES, use weather library (right panel)
6. Use table 43 - historical overrun
7. There are turn numbers 1 to 64 and weather type.
8. It will probably be enough to change weather types from whatever to 3 or 4 but not 1 (clear).
See picture
