nothing earth shattering here but I thought I would give my info. last year in the dead summer when driving on the highway the transmission temp would always get up around 190 - 195 in 95 - 100 degree outside temps. I have read it can get up to about 100 degrees higher than the outside temp under non towing conditions.
anyway earlier this year I had the transmission fluid flushed at the dealer at 55k miles. We have gone on 2 200+mile 1 way trips recently. the last with outside temps 99 - 101 on the way home. The transmission temp peaked at 182, usually at 180 or less. with the cruse at 70mph
I guess the newer fluid keeps things cooler? I don't think we have an external transmission cooler either

 

fluid with less 'gunk' or non fluid materials will perform better... so it's possibly, or maybe you had a small clog before?

 

Interesting... wonder if the original fluid was a different viscosity or was low and the refresh topped it off....look at the front of your radiator and see if you have the small trans cooler mounted in front...
I added the factory one to mine and it seems to knock the temp down about 20-25 degrees from none cooler'ed