it’s about 90 here and we tow a lot is that enough trans cooling?
What are you towing?
ATV trailer w/ two machines? You're fine.
10,000# gooseneck? It might be time to add one.
There's no harm adding a cooler, except the minor risk that you've added a new, potential leak source should it or its hoses fail.
If you're the curious type like me, who wants to know if/why a cooler's really necessary, get a scan tool and watch your trans temps. Prove to yourself whether your driving characteristics, in combination with the trailer load, warrants a cooler.
Or just put one in and move on.
Transmission oil temperatures depend greatly on the driving characteristics.
Moving down a level highway with the TCC locked up isn't going to put much more temp in the trans oil w/ or w/o a trailer; the marginal increased temp would be a consequence of the higher line pressures w/in the trans, and gear loading, in response to the increased applied engine torque. The lack of torque converter slip will forgo a lot of temp rise.
Stop and Go (basically the "go" part) traffic with a heavy trailer will impart much more heat to the trans oil due to torque converter slippage (a consequence of the prolonged, repetitive periods of acceleration w/ TCC unlocked).
Driving in rolling terrain is akin to stop and go traffic, i.e., repetitive trans shifts and periods of unlocked TCC are both adding heat to the oil.