The eastern North America has been under the influence of a heat wave that hasn't quite abated yet. For about 3 weeks now, the daytime temperatures have been hovering around at least 30ºC (what's that on the Fahrenheit scale?).
July 22nd was an exceptionally hot day. At 1545 a few centimeters above the soil in my backyard, I measured an air temperature of 39.3ºC. When I put the probe of the thermistor in contact with the surface of a rock that had been baking in the sun, it shot past 46ºC*.
It eventually went up to 46.7ºC and would have gone up even higher if I hadn't gotten too hot from squatting out there and escaped inside.
My underlying purpose was to figure out how the snails and slugs that normally inhabit the undersides of those rocks were faring with the heat. I could not find any Vertigo to run a test, though. Had they all retreated deep into the soil?
*Admittedly, this was not a good measurement. The thermometer probe, being unshielded, was probably exposed to radiation. On the other hand, it would have been difficult to shield it while measuring the temperature of the surface of a rock.