[quote=“learningmore”]Jamil has mentioned that “rehydrating” dry yeast isn’t recommended, because the yeast is ready to go out of the package, with the right amount of nutrients and cells in order to begin fermentation on a 5-gal batch of beer. Re-hydrating it past the pitching temperature (ie: up to 100 deg) wouldn’t be a good idea because fermenting at high temperatures produces off-flavors most people don’t like.
I agree with you- the shock from going from 35 deg in the fridge to 65 deg in the cooled wort would be a shock, but I’ve never had an issue with it. You may experiment with leaving the yeast on the counter, or putting the closed package into a cup of 65 deg water, then pitching it when you are ready.[/quote]
Making a starter with dry yeast isn’t recommended. Rehydrating is fine, although I seldom do it and get good results anyway.
BTW, putting colder yeast into warmer wort is fine. It’s actually the best thing to do is you have a yeast starter for liquid yeast.