You can buy a weatherproof box cover that is made for use during rain (or when your sprinklers hit it). This type of cover is essentially a semi-dome shape with one or two holes at the bottom.

When you get the cover home, turn off the power to the outlet at the main panel. Don’t just trip the GFCI “test” button. That will kill power to the outlets that are downstream of the GFCI ...

I remember working on a residential remodel project, troubleshooting a front porch electrical outlet that was not working. I first tested the receptacle to make sure there was no electricity present.