You guys are wrong. It is a common fallacy that humidity makes the ball travel shorter. In actuality, it goes very slightly further in higher humidity, since humid air is actually less dense than dry air. Counterintuitive, yes, but its true! The effect of temperature and air pressure (yes the barometer has an effect on how far you hit it!) have a far larger effect on distance than humidity, however.
You can plug in numbers to this page to calculate the "density altitude" or relative density given the altitude, temperature, air pressure (what the web site calls altimeter setting) and dew point. If you get a relative density of 90% with one set of readings and 100% with another, you can conclude you will carry the ball approximately 10% further in the 90% conditions, since the ball goes further in air that's less dense, at least up to some point well above where there are any golf courses.
The gain is slightly less than the 10% indicated because the less dense air reduces aerodynamic lift -- the reason why you have dimples on the ball. But its pretty close, based on my experience just comparing the distance I get at 55 degrees and at 85 degrees. Its probably a bit harder to notice the effect of air pressure, since it isn't something most people know unless they check the weather, or have joint problems, I suppose. I plan to try and see if I can notice the effect this summer by checking air pressure readings after I play and comparing it to my impression of how far I was hitting it. Might explain why one day I hit it a full club longer than two days later at the same temperature.
http://wahiduddin.net/calc/calc_da.htmFor example:
50F / 45F dew / 0 ft / 30.00 in barometer = 101.65%
90F / 45F dew / 0 ft / 30.00 in barmoeter = 94.25%
90F / 80F dew / 0 ft / 30.00 in barometer = 93.38%
90F / 80F dew / 0 ft / 29.00 in barometer = 90.22%
90F / 80F dew / 5280 ft / 29.00 in barometer = 73.99%
90F / 45F dew / 5280 ft / 29.00 in barometer = 74.86%
So if you want to hit the ball like Hank Kuehne, play in Denver on the hottest day of the year when the barometer is really low. You will lose a couple yards on your tee shots since the dewpoint there is more likely to be 45F than 80F, but you'll still be out there pretty good! I chose 80F as an extreme, it is very very rare for anywhere in the US to hit that (silly urban legends about "90/90 days" down South notwithstanding)