How long should I wait?

My date is meant to reach the park for a picnic date in an hour, but he’s driving in traffic. I have a feeling that he isn’t going to turn up, since he’s been ignoring my messages about where to meet and get free parking.

How long should I wait to meet him, before I assume that he’s stood me up and I leave?

Updates
9 mo
He was late, got caught in traffic, but eventually turned up and I think it went well.
How long should I wait?
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