How does one correct a time slip? I've tried searching online and have come up empty handed.
I want to correct for temp, humidity, and altitude.
I think that 85 degrees and 79% humidity can attest to me loosing 2mph?

 

Yes..high humidity lowers the oxygen content of your air charge, so you get slower. High heat also "thins" out the air. On a 95* day, I typically run .4 and 3mph slower than on a 78* day.

NHRA only corrects for altitude, and the charts are on their website. Temperature / altitude / barometric pressure all will change the Air Density Altitude on the particular day you run. To compare apples to apples you would have to calculate the adjustment based on those three variables, then multiply the result times your ET to get the corrected ET. This is where race computers come in handy...like the Performaire. These numbers are helpful for ET prediction and tuning... BUT...

Note: NHRA only corrects for ALTITUDE, so when you see a "corrected" ET, that is the only variable that is taken into consideration.

 

There are a bunch of javascript web pages out there. You also need to know the barometric pressure. Search for density altitude conversions.

As for temperature and humidity it has to do with saturation pressure. There's a lot more water in the air at 85* and 79% humidity than there is at 60* and 79% humidity.

All are relative but you need temperature, humidity and barometric pressure to do the proper conversion. Chances are the air pressure was lower when you lost 2 mph.