There's a whole bunch of ITUN settings for lightning appearing under Sims3.Gameplay.Seasons.SeasonsManager+WeatherManager+ RainEvent, reachable through NRaas Retuner. This is uncharted territory, but it seems to me like it would be okay to experiment with some of the combinations to end up where the chance of lightning for each rainstorm is so small that it almost never happens. Thunder then becomes irrelevant because it has to follow lightning, so if there is no lightning there should be no thunder.
And my second suggestion would be to not buy too much margarine. We didn't know how unhealthy it was back when Mother Nature was complaining about being fooled by it. :)