Because we often have "pop-up" thunder storms in the summer I keep things like my tread mill, sewing machine, etc. unplugged when I am not using them and turn off and unplug my computer any time I am leaving the house. I never know when there will be a thunder storm. Having lost a computer, TV, and garage door opener to a lightning strike, I say unplug!!! (I also lost one of my best friends when she was struck by lightning while taking out her garbage.) Lightning is a powerful thing. Respect it!