They're fine in the summer, just wear a cotton shirt ot t-shirt under it.
When I want your opinion - I'll tell you what it is!
If it got even hotter you'd just wear a shirt.
The shirt has insignia on it as well...
There was a cotton summer shirt available as well.
Hi Tony,
They are a dreadful jacket - colder in the cold and warmer in the heat, but don't let this put you off. 
Seriously they are fine in the summer weather. They are not that heavy with wool, especially if you are not wearing the wool shirt underneath.
In regard to GI's in the summer, they simply took it off. The shirt underneath was the summer Uniform.
Here's a pic of myself and Yith at the Doughboys' game last summer - when it was very warm - in the 'summer uniform'
Hope that helps
*edit - I don't care if other's beat me to it. I was typing and finding a picture 
They are a dreadful jacket...
They also have far too few pockets!!!
But don't let that put you off getting one... they're essential for a GI impression for most of the war!
very much so mate, superb pic too. yeah similar to the airborne then, cold in winter, bloody hot in summer (but still it hasn't put me off)
the shirt then is just the basic enlisted mans then, one more question, i have one of these and hate it if i'm honest its itchy and i just don't get on with it, i wear a t shirt in summer, but was wondering are there any shirts with a good colour match that are not wool i could use as a replacement, even though its not correct, just for comfort more than anything.
Yes and no. they aint right, but they are certainly fine under the jacket. I used/use a British Officer's Shirt, and these days the US tropical shirt - as the wool one caused me no end of problems.
any, preferably dark, Khaki shirt will do. You only see the collar anyway.
There is a khaki cotton shirt:
http://www.atthefrontshop.com/ProductDe ... ode=USUSEK
or you could be brave and wear a tank top:
http://www.atthefrontshop.com/ProductDe ... ode=USUSTT
