I'm not sure if this is dangerous or not but I did it anyway. Our backyard was a little out of control. Its been raining like crazy and the grass was high. . .really high. I can't start the regular mower and it is so heavy to bring down the stairs so I whipped out the electric mower and the long orangeextension cord. It wasn't raining but the grass was a little wet. I figured its a mower and the maker must have taken into consideration that someone would want to mow wet grass so I went for it. . .I kept waiting for the shock or something bad to happen but it seemed OK. The backyard is a little more under control. . .except for the massive amount of weeds. I'm not quite sure what to do about them.