I now have a Samsung Galaxy 6s Active, which is supposed to be waterproof, but for three years I carried an Iphone on the trail. When it was raining I would put it in a sandwich baggie. It weighs 2 grams and cost 1.59 for a box of 50. I could easily operate the phone through the plastic.
To use the headphones I poked a little hole in the bag.
My phone didn’t have an easy life. I dropped it many times and walked through monsoons, showers, hail, and snow and my phone made it through intact.