Best Top Down ED Touring/Timing?

We're entering the purchase process for ED M3 convertible and are receptive to general or even specific advice from "been there done that" ED bimmers re 2 week touring Germany, Austria, East/SE France, Italy especially as relates to warmer than frigid ambients so we can hopefully enjoy a bit of top down driving in the gorgeous countryside. Since our choice involves V8 M3 and we've heard that production is scheduled to end sometime in June, then that's a factor. Fact that snow tires are required up to mid April seems significant. We realize that weather is totally unpredictable, but seasonal trends count for something.