I have a First Gear mesh. It's great when your moving, plenty of air flow. Gets hot real quick when your stopped. Mine is black. That probably doesn't help matters. I can't think of anything that offers protection that would be any cooler. I even tried one of the draggin jeans mesh kevlar shirts, same deal but at least the jacket comes of easy and quick when you stop. The kevlar shirt was uncomfortable as heck.
I am looking into the Olympia Airglide jacket because it is mesh but comes with a separate liner so when it cools off at night you can use it.

 

I'd say yes because the jacket allows air circulation while reducing the amount of skin directly exposed to the sun. And, if you ride in areas of extreme heat check out some of the hydration vests on the market that are worn under mesh jackets. I've never used one of those but I have been known to wet down a T shirt under a mesh jacket to provide some cooling. (Worked great)

 

FWIW, I use a predominantly silver HD mesh jacket with armor in the elbows and shoulders (but no back armor provision) during the spring and hot summer of Metro Atlanta and find it very comfortable. I'm sure if it was black it would work like a heat sink. So consider your color choice--black is great looking, but soaks up heat. The HD mesh is not a Power Ranger pattern.

 

I have a First Gear mesh jacket. It quickly became my jacket of choice. Cool in the summer when you are moving. I think it is cooler than just wearing a t-shirt. Have had mine for 3 years and it is still like new.

 

I really like my Olympia mesh jacket with zip out cold/rain liner. Keeps me cool in hot weather and comfortable down into the 30's with the liner. First rate product.

 

I dont have First Gear (mine is Tourmaster) but I can definitely say that Mesh jackets BREATH like you wouldn't believe - even stopped at a traffic light if there's a breeze blowing you can feel it passing thru the mesh. So at speed you'll feel like you're in a t-shirt believe me.

 

I have a First Gear mesh and really like it.

I wear it on even the hottest days without the dry liner and I stay more comfortable than if I had short sleeves, if I'm riding on the highways or open roads.

In town on city streets in summer, you're going to sweat your butt off around here no matter how little you wear or what you ride.

 

I have a First gear mesh and it works great. Wore it all day during a 625 mile day in 90 to 95 temps. Stopping often for hydration.

 

I use a First Gear mesh jacket when the temp hits 80, otherwise a leather jacket. They are fine when you are moving, but will heat up when stopped in traffic...that's to be expected. Be sure to get the armor pads.

 

I also have the FG Mesh Tec II, like very much, has the removable liner for cool nights and rain. I also have a cool vest, one you soak in water....these will keep you cool along with the mesh jacket. When I road to CA on my 06 UC, it was cooler with the mesh jacket and a full face helmet than a t-shirt and a shorty helmet...126 degrees in AZ....it was warm.