Operating a pressure washer is pretty straight forward and it does require a bit of common sense. First, you do not want to get your limbs or eyes in front of the nozzle. It also makes sense to be aware that the deflected spray, especially with narrow degree tips can be dangerous as well. That is all common sense, and anyone who has ever used a pressure washer knows that much.
What about other dangers? Such as; can you safely use a pressure washer in the rain? And if so, should it be covered? Well, first you must realize that pressure washers are tested for such things to protect consumers. So, check the UL rating and if it does not say UL on its label then do not use it in the rain. Pressure washers are known to be used in a wet-environment and are tested for salt-spray and electrocution.
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Over the years, I've used pressure washers and steam cleaners in the rain and never had a problem, of course, this was well before all the Chinese Pressure washers, and little electric personal pressure washers hit the markets. Many of them are not UL Rated and I would not advise using them in the rain. Still, to protect your equipment it's best to have your pressure washer in a place where it will not get wet, and enough hose to get to where you need to work.
If it is raining hard, you can always put down the tail gate on a pick-up truck and put the pressure washer underneath it while it is running. Perhaps you might consider this.
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