How do I find out if the view is good at Hancock Tower today?

I would say, find out the sunset time for today. Go just before that. Plus point if there's clear and sunny weather.

Weather report is your friend.

Check the weather report, just make sure it is not cloudy.

Look up

That is your best bet cause if its cloudy not worth it .

GOOGLE.. Chicago weather in Gold Coast. If not cloudy, then you're good.