What would be an alarming transmission temp?

Since I've got the ScangaugeII running and reading it transmission temp I'm curious what is considered high or abnormal?

I'm currently sitting at around 82 degrees Celsius. (180F).

 

250ish I would think

 

Seems like @gearcruncher has mentioned a temp before that is pretty much the point of fluid damage/mechanical damage.. can't recall.

 

Referring to a 2nd Gen auto trans:
https://www.tacomaworld.com/threads/transmission-max-temp-toyota-answers.279990/

We apologize that the Owner's Manual does not include the temperature in which the automatic transmission oil light will illuminate in your 2013 Tacoma.
If you are towing with your vehicle, the automatic transmission oil temperature light may illuminate at 302 degrees. If the light comes on, it indicates that the auto transmission fluid temperature is too high. If the light flashes, it indicates a malfunction in the auto transmission system.

 

My F150 runs around 185-190 for normal driving (once it's up to temp, at least. Takes about 30-40 minutes of driving to get there) Towing a bass boat this fall it ran between 195-205, depending on the terrain. Modern transmissions with efficient coolers have to work pretty hard to get into the 'danger zone' as far as temperatures go, as long as you keep the fluid fresh and keep it out of OD while you're towing.

 

I thought running close to water temp was high but I guess not lol. So Im in a safe zone

 

You are correct that the light on the dash comes on far too late . At 302 degrees , you have basically cooked your transmission fluid and almost guaranteed damaged internal transmission components .
Keep in mind if you overheat your engine , you have also overheated your transmission . Why does this happen ? because the transmission is heated and cooled using the engines cooling system .
Taking the truck for a mud run in 4x4 low , youve got little to no air movement through the transmission cooler , stop and go traffic as well as towing also heat up your transmission very very quickly.
This is why I push members to purchase either a scan gauge or ultra gauge and try their best to keep the transmission temps under 200.
What we have found after members purchased either gauge is they then realize they will be needing a larger transmission cooler
Here is a recent transmission cooler install with some pics
https://www.tacomaworld.com/threads/aux-transmission-cooler-diagram-pic.324202/