The famous weather generator mod by ArtOfDrifting.
It adds an extra challenge to the simulation, as it makes conditions drift from dry, to light, then heavy rain or vice versa. With a little practice you can create minute-by-minute weather conditions.
Works with GTR2 default cars, and even better with P&G v3 (as many cars there have all weather tyres).
Great little mod, works well and doesn't cause online mismatches.
Please read the instructions in the README.TXT
All credits (and thanks) got to ArtOfDrifting (Ivan Witteveen) who has continuously developed this tool.
The latest known version is the one presented here.
NOTE: this tool/program requires Java (at least version 1.4). It will automatically detect whether you have this.
If not, it directs you to www.java.com where you can download the latest version.