As a citizen of the USA, I can tell you that for whatever stupid reasons we haven’t adopted standard units, it’s so low on the priority list that even those of us who would really like to see that happen aren’t going to spend much effort on it. And because we’re a large, insular country, there is very little pressure from anywhere to do so.
When I was growing up in the 1970s, there was definitely a sense that we were transitioning from Imperial to Metric. States on the Northern border (Southern too?) had speed-limit signs in both miles-per-hour and kilometers-per-hours. Bank signs (which for some reason always had the current temperature) had both Fahrenheit and Celsius. Many food packages reported quantities in both ounces and grams or cups and liters.
But at some point most of that stopped. Slowly I think. The roadsigns are gone. Temperatures everywhere are reported only in Fahrenheit. Foods are generally packaged again in Imperial units… although there is an interesting carryover of 2-liter bottles and often fine print with equivalent metric units.
With the major problems currently besetting the United States, I can’t see a units transition becoming a major agenda item soon. That’s too bad, but not a tragedy. It’s easy to understand why Americans, who rarely hear any other units, report only their common ones, which is why certain people only report Fahrenheit.
Of all the unit changes we could make, Fahrenheit is probably the one I’d worry about least. I like the additional granularity of the Fahrenheit degree, and both scales seem to be built on the same misconception that temperature is a cycle, hence “degrees” for a unit. (I’m sure I read that about °F; I don’t know for sure about °C, but it seems likely our why keep with “degrees”?).
So good luck with your heatwave. I’m with @Springer in feeling better prepared for terrible cold than terrible heat, so stay safe. But just remember that if you were in the U.S. for a heatwave, you’d be discussing temperatures such as 100°! 40° doesn’t sound too bad in that context, right?
