How can I prevent moisture from damaging my tools overnight?
As you said, until the tools warm up, you will have condensation problems. Cold tools and warm air will always give you condensation problems. The only option is to prevent your tools from getting that cold.

Using heat to protect expensive/precision tools is nothing new and is commonly done to preserve firearms. I use this GoldenRod heater type dehumidifier http://amzn.to/2utHyWQ to protect machine tools with exposed metal surfaces like lathes from the dangers of condensation corrosion. 
I have even seen these heater bars used on pianos to protect the wooden structure.

I suggest you place them in or under your tool racks and leave it plugged in overnight. These simple resistance heaters can also be hooked up to a 12v line, though it would most likely only output 10% of the original amount of heat when done so.

Then again most of my hand tools and even the vast majority of my power tools seem to be unaffected by condensation/moisture/rain. The only things that get their own heater are the expensive precision tools and measuring devices.