60 mph is quite bad enough!
Mixing units can happen to anyone. According to one report released after an investigation, one of the joint NASA/ESA Mars landers crashed because NASA was using metric measurements while ESA had decided to use imperial.
On a more local note, at least the week of drier weather gave me a chance to strim the top off of most of the lawn. There’s no way I could have used the mower on it, though. I’d just have just ripped the grass out by its bedraggled roots.