I can vouch for the night temp drop thing. I moved recently and thought "Great, it's hot and steamy here, the neps will love it!"
OOPS, with daytime temps reaching 100 F and 95% humidity the plants did great, but after a few weeks of 90 F nights, the highlanders were definitely affected. They all seemed to be happier in the dryer 78 F AC air in a north window just watching the heat outside. I believe the sun raises the temp just enough for them during the day. They are outside now during the spring, but I will swap them with lowlanders in the summer.