High temperature effect on distance?

I've read in the forums here before that high temps in humid weather give you more distance. Is this true? I played my best round of the season today on the hottest day (heat index 108) of the year too. I was hitting the ball considerably shorter and it felt strange at contact. I was having to hit one club stronger than normal. This is my home course, so I'm familiar with what I normally hit where.

Maybe the heat was having a greater effect on you physically. I know that sometimes when it's really hot out, my arms feel heavy and rubbery.

I don't think that hot weather has nearly the effect on the distance a ball travels as cold weather does.

I agree with this. I played in 100º+ heat index last week and never really felt right, and it showed in my performance. I am not one who get bothered by the heat much at all, but this particular day got to me. The ball should fly better in hotter weather. I might not be very noticeable, but it won't be a club shorter, something else would be in play.

Their is much less oxygen in the air when its humid. THus the reason airplanes need more runway for take-off when its hot & humid vs in a dry climate.

Temperature: Air becomes lighter as temperature increases; warmer air also rises more than cold. That translates into less resistance to ball flight, reducing drag and lift, resulting in lower trajectory and minimizing slices or hooks.

Humidity: A yard or two span between completely saturated to bone-dry air. For elite players seeking distance the goal is shirt-soaking humidity: Dry air is denser and causes more drag, reducing ball flight.

Higher temperatures = lighter air density, also the ball warms up and becomes more elastic.

Heat index has nothing to do with temperatures, especially when it effects the golf ball. Heat index takes into consideration dew point and humidity. Of course a drier air will be a bit longer than humid air, but not as much as playing in 75° weather and 95° weather.

I can't remember, i think its something like 1-2 yards per 5°. So if you normally hit 250 at 80, than you will hit 256 at 90. I think what really kicks in is drier golf course, so more roll.

Most people who haven't studied physics or chemistry find it hard to believe that humid air is lighter, or less dense, than dry air. How can the air become lighter if we add water vapor to it?
Scientists have known this for a long time. The first was Isaac Newton, who stated that humid air is less dense than dry air in 1717 in his book, Optics. But, other scientists didn't generally understand this until later in that century.
To see why humid air is less dense than dry air, we need to turn to one of the laws of nature the Italian physicist Amadeo Avogadro discovered in the early 1800s. In simple terms, he found that a fixed volume of gas, say one cubic meter, at the same temperature and pressure, would always have the same number of molecules no matter what gas is in the container. Most beginning chemistry books explain how this works.
Imagine a cubic foot of perfectly dry air. It contains about 78% nitrogen molecules, which each have a molecular weight of 28 (2 atoms with atomic weight 14) . Another 21% of the air is oxygen, with each molecule having a molecular weight of 32 (2 stoms with atomic weight 16). The final one percent is a mixture of other gases, which we won't worry about.

Molecules are free to move in and out of our cubic foot of air. What Avogadro discovered leads us to conclude that if we added water vapor molecules to our cubic foot of air, some of the nitrogen and oxygen molecules would leave — remember, the total number of molecules in our cubic foot of air stays the same.
The water molecules, which replace nitrogen or oxygen, have a molecular weight of 18. (One oxygen atom with atomic weight of 16, and two hudrogen atoms each with atomic weight of 1). This is lighter than both nitrogen and oxygen. In other words, replacing nitrogen and oxygen with water vapor decreases the weight of the air in the cubic foot; that is, it's density decreases.

Wait a minute, you might say, "I know water's heavier than air." True, liquid water is heavier, or more dense, than air. But, the water that makes the air humid isn't liquid. It's water vapor, which is a gas that is lighter than nitrogen or oxygen. (Related: Understanding water in the atmosphere).

Compared to the differences made by temperature and air pressure, humidity has a small effect on the air's density. But, humid air is lighter than dry air at the same temperature and pressure.

Effects of air density on airplanes, baseballs, race cars
More dense, or "heavier" air will slow down objects moving through it more because the object has to, in effect, shove aside more or heavier molecules.

Such air resistance is called "drag," which increases with air density. Baseball players have found that home runs travel farther in the less dense air in high-altitude Denver than in ball parks at lower elevations. The reduced drag slows the ball down at a slower rate, which means it travels farther. (Related: Why baseballs fly farther at high altitudes).

Cool, dense air slows a race car, but some race cars gain from dense air. Cars designed from the wheels up for racing are really like upside down airplane wings that the air pushes down on the track, increasing their grip going around curves. Denser air pushes then down harder. (Related: Auto racers' winning equations include weather)

Aircraft pilots don't do as well as baseball players when the air's density decreases. Lower air density penalizes pilots in three ways: The lifting force on an airplane's wings or helicopter's rotor decreases, the power produced by the engine decreases, and the thrust of a propeller, rotor or jet engine decreases. These performance losses more than offset the reduced drag on the aircraft in less dense air.

Pilots use charts or calculators to find out how temperature and air pressure at a particular time and place will affect the air's density and therefore aircraft performance. In general, these calculations don't take humidity into account since its affects are so much less than the others. When the air's density is low, airplanes need longer runways to takeoff and land and they don't climb as quickly as when the air's density is high.

Air density also affects the performance of automobiles, with lower density decreasing performance in the same way it decreases the performance of aircraft engines.

Turbochargers or superchargers are ways of increasing the density of the air going into an engine. The give autos more power on the ground and they allow aircraft to fly higher into thinner air than they would otherwise.

Pilots use "density altitude" to relate air density to aircraft performance. For more about density altitude, you can read an article I did for the Aircraft Owners and Pilots Association's Flight Training Magazine in July 2003 on Why airplanes like cool days better)

I had the humidity discussion on the course yesterday. It was really humid, even more so than a "normal" day in Florida. All our drives seemed to be going farther than normal, so I mentioned to my playing partners that it must be due to the humidity. They both pooh-poohed me, saying that OF COURSE humid air hurts distance rather than helps it. One is a science teacher at the local HS and the other works for a Continental Airlines maintenance shop, so they should have known better. I gave them the "hydrogen atoms are lighter than Nitrogen atoms" reasoning, but it didn't convince them. Then I asked them "Why does steam (visible water vapor) rise?" I think it finally sunk in, although they said they would have to check it out for themselves. For the rest of the day, the comment on every teebox was "Watch this. I'm really going to hurt those hydrogen atoms with this one!"

I fully understand the concept that humid air is lighter then dry air. On a practical level though, it seems the ball goes less distance in humid conditions for me and the group of guys I play with. I'm not just sampling the summertime hot/humid days, I'm talking overcast spring/fall days as well.

Hard to say since there are so many variables involved, but could the humid air (although lighter) actually produce more drag?? Is there something along the lines of "viscosity" for gas, that is independent of density?

When I play in hot humid conditions the ball seems to go farther than during hot less humid conditions.
Some days, just after a hot evening shower when the air is unbearably humid I get an extra club difference in length on my irons.

Carry distance != total distance. Humidity will only help carry distance, but if the ground is really dry and running fast, then that distance can easily be made up with in roll.