Why as a matter of fact the back of my neck is feelin' dirty and gritty

We've broken a record here in Tokyo this summer for longest heat wave on record locally - 38 straight days in which the high temperature has been above 30 C (86 F for all those living in the stone age), including a record high temp in July of 39.5 C (103 F) and a record hot low of 32 C at 4am a few days back. And all with humidity in the 75 to 95 percent range. As they say in Texas "It's hotter than two rats fucking in wool sock around here"