can I open Screen bottom board?

[Bill Jackson]

I'm using an upper entrance and have a SBB. At what temperature should/could I open my SBB and how much?
I also have a summer screen(3/4"X 16" facing back of hive) at the top of my supers to provide a draft in the honey supers.

[Ross]

Mine stay open pretty much all the time. I have found that early spring build up is improved a little by blocking them from the wind. I'd say if it's warm enough for the bees to fly, you're more than safe to open them.

[Michael Bush]

I open them when they start to beard and close them at the first hard frost.

[Bill Jackson]

Thanks guys