Checking out flight status on
www.cathaypacific.com, and for
CX 807 ORD-HKG on 28 June, there was a note "Please be advised that CX807/28JUN is delayed until 4:10pm local time due to high temperatures in Chicago. Check-in closes at 2:45pm local time. We apologise for any inconvenience caused", and then a re-route to TPE.
So how exactly does temperature play a role in aircraft delays and reroute?