Should add, I've also lost air-con to a server room at a later job due to the weather. This time I was working at a University and was in charge of a small server room for one of the departments. During winter, I came in one morning to find the room like a sauna and the air-con system pumping out warm air.
The reason was that the external air-con units had been mounted on the ground outside (this was a first-floor room) as it was cheaper than running chiller pipes up to the roof. The building had a sloped roof, and we'd had some snow a few days before. As the snow began to melt, a huge pile slid off the roof and buried the external units which promptly tripped out due to the sudden lack of airflow. And just like that, every air-con unit stopped and up rocketed the temps!