You might consider this
I suppose you are familiar with the field method of computing Density Altitude, namely: multiply the difference from standard temp by 120 & add to PA (or what altitude is showing on the meter...it's close enough). e.g.: 1000' showing on the meter & 35 C; that's 20 C above standard; 20 x 120 = 2400; 2400 + 1000 = DA of 3400 ft.
Well, humidity has an effect on DA and a "field" method is to add 100 feet for each 10% of relative humidity, on top of the DA already computed; e.g.: 3400 ft DA already computed, with 80% relative humidity, makes another 800 ft of DA, or: 4200 ft.
If it feels really "sticky" outside, just assume 100% humidity & add a thousand feet to your temp-computed DA; this is a very inexact "science," after all.
This trick may prevent your being "surprised" in the future. Best to you.