As a person who enjoys filming outdoors, especially during severe weather events, and having seen lots of videos on YouTube about severe storms including derechos, downbursts, and even a few tornadoes,I have developed and invented a way that everyone should use to keep all that rain out of their camera while filming, so you don't have to retreat so far back when the rain starts pouring down.
Usually, blankets, bed sheets, and sometimes even towels, come in those zippered transparent plastic bags, especially at the store. If you have recently bought any of those items that came in one of those plastic bags, instead of tossing the bag, you can use it to keep your camera dry in the rain.
All you need to do is put your camera inside the plastic bag, zip the bag closed, and you will be great to go film the next severe weather event, as long as of course you don't stand close to or downwind ofany big trees lest you get hit by falling tree branches! And neither should you be on any hills lest you get struck by lightning.
I do however need to say this, if there is a tornado warning, you should be indoors, preferrably in the basement, as especially the middle of the country far from any large bodies of water does tend to have a lot of very destructive and violent (F-3 and stronger) tornadoes.