US January-May temperatures have dropped over the past forty years and particularly over the past twenty years.
The last three January-May periods in the US have had the least warm weather since the start of the 20th century.
In order to hide this, NOAA has adopted a new algorithm over the past five years where they simply add huge amounts of additional data tampering on top of their normal fraud.
The tampering is particularly bad for maximum temperatures.
Until 400 PPM CO2, the data tampering used to track CO2, but even that fraud wasn’t enough to keep up with the cooling, so they have adopted new tactics.