Up here in Ontario, the mercury is starting to dip below freezing overnight, and it is time to start thinking of the workshop, and what you should do to protect it for winter.
When your workshop will be exposed to these temperatures, you should bring in all your waterborne finishes and glues. Finishes that are alcohol or oil-based should not be a problem outside, however do read the labels. Wood filler, though usually oil-based, should be brought in as well.
As far as tools go, there are two problems that you may encounter. The plastic casings for many tools are hard however they expand and contract differently than the metal they may be attached to. When this happens, the plastic is prone to crack when it freezes, or even thaws.
The other danger is moisture! Warm air can hold more moisture than cold air. When a tool is cold and a warm breeze passes over it, water will tend to condense on its surface. Just look at your ice-cold drinks on a hot day, and you will see what I mean. To protect your tools from rust that will form on metal surfaces, give the tool a "second skin" that will let the moisture bead up on. Put your tools in a tool chest, box, or other storage area that is relatively sealed, but not completely. You want to allow the entire container to warm up at the same rate, without actually stopping the air from entering.
As a further suggestion, put a desiccant in with the tool in the container. A desiccant is a substance that can absorb the water from the air, and trap it in a form that won't endanger your tools. Silica gel is the most common desiccant nowadays, and a cheap source is premium cat litter. The silica gel looks like opalescent beads, whitish but almost translucent. Simply wrap a small amount in something that can breathe (nylon stocking, or even a regular stocking) and place in the container with your tools.
Of course, simply bringing them inside is the best option. Just be sure that if the tool is already cold when you bring it in to wrap it with cloth as it warms up, to prevent the moisture from condensing on the surface of the tool.
Now there is no excuse to find rusted tools in the spring!