I've heard alot of people say that hair grows faster in the summer or in warmer climates...does anyone know if that's true?  Why is that?  If so, is it heat, light, UV rays or seasonal changes in daylight that promote growth?  Does spending alot of time indorrs make your hair grow slower?Could spending more time outside increase growth?  Just curious what you guys think.

A few of the theories on hair growing faster in the summer:

1.  Warmer temps stimulate the hair folicle more.
2.  Cooler temps cause constriction of the blood vessels on the scalp, reducing hair growth.
3.  Warmer temps = faster metabolism = more hair growth
4.  People are more active in warmer temps which then stimulates blood flow.

I know that my hair grows slower in the winter.

I agree  :).  My hair does grow faster in the warmer temps than what it does during the cooler.  Yea for warmth  ;D ;D.

Debr

Personally, I find that whole theory to be a bunch of nonsense. Last year, I tracked my hair growth every month and found that temperature/climate had nothing to do with it. I actually got more growth during the colder months on average. Of course, I am rather strange...  ::)

I wonder if it also depends on the person. Before I moved from Hawaii to Japan, I was concerned that my hair growth would really slow down during the winter, but that hasn't really happened. I've still been averaging a half inch per month.

I don't really know. I live in north, and my hair still grows in quite a normal rate. We have shorter summers, but my yearly growth rate is still normal.
Also, my hair had its latest big growth spurt last fall. Based on my recorded measurements, my hair seems to grow quite steadily throughout the year and growth spurts/rest periods are quite evenly distributed.

BB's ideas sound quite good, so just for fun, here are some things that could countereffect them

1. In winter, you spend more time indoors where temperatures are steadily warm, and often a little warmer than outdoors (from my Northern perspective, anyway)
2. Agree, so the question is, how much are you exposed to cool temps? If you go outdoors wearing a good hat or other warm headcovering, it is likely that your scalp will be quite warm.
3. Faster metabolism: sauna must promote hair growth!  :P Hmmm... a good excuse to warm the sauna three times a week?
4. If you go out in a cold weather, you need to be active just in order to avoid freezing. In cold temperatures, the body can also produce extra heat by shivering etc. The energy consumption of the body is significantly higher in cold temperatures => the body needs fuel to retain/generate heat, which means that even in rest, the bodily functions are active and therefore, the metabolism should also be more active in order to keep up => so the hair should grow faster.

Logical, isn't it! Now, where are the pictures of beautiful, flowing locks of Eskimo women?  ;)

Excellent logic, Galadriel!

Now can you explain the winter layer of fat that we northerners tend to put on during winter?  

That, of course, is necessary to keep us alive in case someone steals our coat.  8-) It also helps us to float in case we fall through ice while taking a walk on a frozen lake.

[smiley=smiley_up.gif]  ;D LOL  ;D

Good answer!