Have you tried these?

[PamNY]

TE sells arm coolers. I just got some and love them so far.

[OakLeaf]

+1 on the DeSoto arm coolers.

They fit kind of odd IMO, but if you can get them to stay up, they prevent sunburn and keep you cool.

[zoom-zoom]

I <3 my Moeben sleeves!

[Catrin]

But doesn't it make you hotter to have the long sleeves on?

[Crankin]

One of the couples from Australia wore these (not sure which brand) on our tour in Spain, when it was like 95 degrees. I am sure they were sun experts, given where they live, but they both looked totally red in the face and hot wearing those things in 95 degree heat. I never get burned, even though I am fair, from good use of sun block. One of the best strategies I have found is to put it on well before going out... up to an hour.

[maryellen]

I have a few pairs of white arm coolers--I use them to avoid sun exposure. I don't know that they make me feel cooler but they definitely do *not* make me feel warmer.

But if you pour water on your arms w arm coolers on, you will definitely notice a delightful cooling effect--at least until they dry off!

I did a ride on the W&OD in late May on a brutally hot/humid day and at every water opportunity I stopped, poured water over my head and over my arms. Kept me going until the next water spot.

[Pedal Wench]

I've used both the DeSoto armcoolers and the Pearl Izumi's. The PI's provide more protection from the sun, and aren't noticeably warmer. Just keeping the sun off my arms made it feel cooler than wearing nothing at all. Plus, they stay up more securely than the DeSoto's.

[PamNY]

But doesn't it make you hotter to have the long sleeves on?

Catrin, they don't make me hot at all. You can feel the breeze through them. And pouring water on them is divine.

[TrekTheKaty]

My husband has gotten used to my silly outfits--buff, TE jersey, but white-long-sleeves in SUMMER? He rode a little farther behind me than usual.