Someone mentioned on here last year that external temps need to get below -5 before your pump will be damaged, this concurs with my 20 odd years experience, I parked up in Nottingham one night when it dropped to -10, I had a couple of quilts wrapped round the machine, the fluid in the pressure gauge froze but no other damage, make a habit of draining all hand tools and wands off at this time of year, several times I've had to replace brass valves that have frozen and split on tools