Can the cold water temperature be affected by the hot water heater? I have a tenant complaining that the cold water is barely cool. I keep thinking it is the hot weather we have been having, but I am wondering if it is something more.

I have the same problem here in Florida. Our water services are only 3 feet under the ground level and picks up the ambient temperature before it hits the house system so the cold water's warmer in summer and colder in winter.
Also, if the water heater cold water supply is close to the cold water main the water in the main could be warmed by convection. Regards, Tom

Tom's totally correct. In Illinois our water lines must be at least 48" down to prevent them from freeezing in the winter. Outside temp can/will affect water temp. Where do you live and does your house have the same problem? If you are both in the same town and you don't have a problem then it may be something else.