Monday - Friday 9 am - 2 pm. Typically Mondays are the least busy for schools attending.
I recommend just getting there at 9:00 a.m.
Weekdays are less busy than weekends, but there are local schools doing field trips all day. I'd bet it's less crowded when it's too late in the day for a field trip or around lunch time. However, we usually just go in the mornings during the week and it's not too crazy.
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