I have found mornings are best. I work extremely flexible hours, all over the state, so I like to go to different amps to hopefully get a different/better experience that previously visited amps. It’s rolling the dice, but I’m a gambler. The few times I went late night I felt rushed, like they wanted to end a long day.
The idea of going during a storm seems like a good one, they will no doubt not be busy, and perhaps go the extra mile, appreciating your business a little more.
Just my opinions.