There is a massive difference between 'hottest day of the year' and 'hot'. It may have been one but it certainly wasn't the other, nor has it been cold at night.
As for coping, two days worth of widespread disruption due to one issue would suggest not.
Typical of Southern - their communication and customer service standards whenever something like this happens are shockingly bad, but of course they don't care because they know that so many people are reliant on what they laughingly call a service to get to and from work so have no practical...