The highest temperature ever recorded was in Death Valley, in 1913. [1] Hence the reason for this weird 'at midnight' metric. It also holds another pretty neat record of having 43 days with temperature over 120 each day. That was in 1917. The planet's definitely warming up, but seeing every single freak weather occurrence, let alone in an area uniquely geographically situated for such, as a 'sign' of the end times isn't going to serve much purpose.
[1] - https://en.wikipedia.org/wiki/Death_Valley