Does anyone know which weather website are the best ones to use (to figure out what clothes to pack) for: Cologne, Baden-Baden, Murren/Lauterbrunnen Valley, Munich, Salzburg, Lake Halltatt, and Vienna? We'll be on the RS tour beginning in Cologne on August 19th. I know that's a lot to ask for, so I'd be satisfied with just the best website for Murren weather (although I know it's easy to check daily at most places on the day of).
I use timeanddate.com/weather
Play around with it by inserting place names and getting past weather, plus a 14-day forecast.
the best website for Murren weather
https://www.meteoswiss.admin.ch/local-forecasts/muerren/3825.html#forecast-tab=detail-view
Weather in mountainous areas can be highly unpredictable, so use this as a general guide and check for updates just before heading out for your planned activities.
use Google to find a couple and compare (frankly they probably all get their info from some government entity)
Weather apps are definitely not all the same and things like Google, AccuWeather, Weather.com, time and date.com etc are not at all accurate in the Alps. For Switzerland and Austria we cross check MeteoSwiss, MeteoBlue & Bergfex apps + check webcams for specific sites to get the most accurate picture possible. Nothing is perfect, but those are your best options.