Day/Night temp difference

What is everyone's preference when it comes to day and night temp difference? At the most my difference is 15 degrees. Some say that is asking for trouble with disease but I haven't had an issue with it since my humidity is kept in check. I gave the same advice to friend who is growing and he got powdery mildew. Not sure if I'm doing something right and he is dirty or what. I found some info but it all could be anecdotal. I like keeping it cooler at night especially during the winter because it saves me cash. What are some preferences and/or experiences with keeping temps close or a bigger gap?

Ive got 15deg fluctuations too, never had a problem. 15 night, 30deg day is normal for me. Once you have good extraction and air circulation then you shouldn't have a problem really.

Keep your VPD in check and keep your air moving.

madra said:

Ive got 15deg fluctuations too, never had a problem. 15 night, 30deg day is normal for me. Once you have good extraction and air circulation then you shouldn't have a problem really.

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I've always kept it cooler but ever since my buddy ran into pm problems it's starting to concern me. There also might be some variables that he isn't telling me. Not really sure how healthy his plants are to begin with. I like it because it saves me cash and brings out the purple in some strains as well

PM spores germinate at temperatures between 60-70 degrees with relative humidity of greater than 60% and dry foliage. Your friend might not have as good a RH control or have pockets of stagnant air where these conditions are met.