What extension cord should I use for outdoor power tools?

Get a 12-gauge cord, as short as you can get away with. Thinner cords (14- or 16-gauge) drop voltage over distance, making tools pull more current and heat up the cord. A 100-foot 12-gauge cord still drops some voltage, so buy only the length you need and don’t coil excess. Make sure it’s rated for outdoor use (look for “SJTW” or “STW” on the jacket). When in doubt, go thicker—it saves you from replacing tools later.