When I was competing, I would run 120 mpw in the Texas summer heat during my buildup. I would meet up with my team at 7am and knock out 18-22 mile runs that started out 80 degrees all the time.
Yet...I completely agree with this decision to cancel.
6 years I ago my now wife was racing in a marathon in conditions very similar to the ones forecast to today. She is very good about taking her water and nutrition breaks, and that day was no different. The race started in the high 60's and felt quite cool to us at the start. She felt great and was stopping regularly at water stops. However once the sun came out, everything went south and before she knew it, she was feeling dehydrated and lightheaded.
The last thing she remembers from the race is seeing the finish line in front of her and then everything went black and she woke up in the hospital. She was experiencing rhabdomyolysis, and her temperature had gone up to 107.5. She was touch and go on her way to the hospital (EMS called her father to tell him she might not make it), and we spent the next 3 days in the hospital before she was discharged.
A single person's life is much more important and valuable than a wasted plane ticket, or the inconvenience of spending money on a hotel while taking time off from work. If the medical team Twin Cities was working with decided conditions were dangerous, then the race organizers made the right call. They most likely saved lives today.