Joanna Stern, reporting for the Wall Street Journal: One of the biggest findings of my multi-city 5G review tour: The Samsung Galaxy S10 5G isn’t reliable in the summer — unless, well, you summer in Iceland. When I ran tests, the phone’s 5G often switched off due to overheating, leaving me with a 4G connection. Cellular carriers demo-ing or testing the phone have taken to cooling the devices with ice packs and air conditioners. The phone does this when the temperature reaches a certain threshold to minimize energy use and optimize battery, a Samsung spokeswoman said. “As 5G technology and the ecosystem evolve, it’s only going to get better,” she added. But there is good part, too. The report adds: After nearly 120 tests, more than 12 city miles walked and a couple of big blisters, I can report that 5G is fasten-your-seat-belt fast…when you can find it. And you’re standing outdoors. And the temperature is just right. As my findings show, 5G is absolutely not ready for you. But like any brand new network technology, it provides a glimpse of the future. “Holy spit!” I said the first time I saw a speed test hit 1,800 megabits per second on Verizon’s network in downtown Denver. […] Don’t speak megabits? I downloaded the whole new season of “Stranger Things” from Netflix — 2.1 gigabytes of video — in 34 seconds. The same averaged more than an hour on my 4G connections. And I downloaded a huge, 10GB file full of video and images from Google Drive in 2.5 minutes.