Can temperature fluctuations affect audio gear?

Don't know about this...some owner's manuals say that you should allow equipment and tubes to warm to room temperature before using them, but this is different. My audio room is upstairs, isolated from the thermostat. Have to keep the door closed so the dogs don't venture in there and create havoc. Hence, in summer, the temperature in the room regularly goes to 85 degrees or so. In winter (like now), it will easily drop below 60 degrees. No need to worry about equilibration, since the gear is always in there, but should I worry about the temp fluctuations? Could get a baby gate to keep the dogs out, then it would stay 70-72, but otherwise, in winter a space heater is the only option.