[yrb]

I don't know where on earth you got those numbers for Houston from... that would be a world record by an amazing margin. Very few places to date have recorded wet bulb temps above 35 degrees.

I can only assume you are putting incorrect readings into the calculators.

Are you making sure to put the temperature at the time of the humidity reading, since they reach their maximums at very different times of the day. If you just put max temp and humidity readings for a day in you are going to be wildly wrong.

[somenameforme]

This could well be it. It never really occurred to me how radically the humidity changes throughout the day. I suspect this is because as the humidity rises the temperature is in a low and vice versa. So it feels like a relative equilibrium, but it's not. It'll be interesting to check out the by-the-hour data the next time a particularly mean hot+wet window emerges.