[Pistol Pete]

There's a website called: airdensityonline.com
It will give you the water grains, temp, humidity, barometer, corrected altitude.
Just look at the list of tracks & select what track your at.
Usually updates every hour.
What i've been told is: the less water grains the better you'll run.
One thing to definitely look at if you race in the summer months.
Keep a log book & write down all of the info when you race, also the time of day.

Hope this helps you.