Well, let's see ... a few examples ...
There was a 1200K randonnee attempt out of Davis California where the daytime temps went over 40C. I dropped out of the ride at the 400 km point because I had slowed to a point I couldn't make the next control.
There was a wind in Winnipeg (where else?) which was clocked at 160 km/h and took out a fair across the river from where I was cycling. Knocked me of the bicycle.
There was the century I did at -32C one February ... also Winnipeg.
And a 600K I DNF'd at 300K after riding those 300K in torrential rain and roaring wind. Bridges behind me were being washed out (I found out the next day). I was pedalling hard down hills to get my speed up to about 16 km/h the wind was so strong. When I reached a section of road that ran along one of the main highways, the walls of water kicked up by the passing semis left me feeling like I was going to drown. Then night feel, hypothermia set in, and at 300 km, I was shaking uncontrollably and throwing up. That was the end of the ride.