AC Drive Heat Sink Temperature

Danfoss would be the only reasonable source for that information as it depends on how all of the components inside are designed and selected. i would say that if they have a heatsink trip setting of 85C, that would indicate the maximum allowable. Anything below that would likely be OK.

Isn't this information listed in the manual or application notes?

...and in its absence, how about a telephone call to Danfoss for advice? It would, after all, be quicker and more trustworthy than to wait until the correct data to show up here.

I have used the Danfoss drives several times so I called up a stored pdf of the operating manual. I now understand your question - environmental operating conditions are not given in the manual, at least not for the FC301 series I use.

That seems to be a rather high temperature for electronics. I know the Allen Bradley drives can't be run that hot. Better ask Danfoss before trying this.

You also need to take into consideration the direct sunlight heat loading, ambient temp & how big the enclosure is plus the rate of air flow at present.

Look at the manual, find the heat losses add 10% for other equipment/components and add to that the direct sun light heat loading.That will tell you how hot your drive will get!

now if your cals are near the temp limits, consider a sun shade, that will remove most of the sun light loading, then larger fans.. then a small compact low power A/C unit.

All these steps I use in the desert, so I know they work

We have such a unit. Make sure that the cooling fan for the heat sink is working. (It's not very accessible) We had a capacitor for the motor blow and then the cooling fan motor went bad. That's mainly the reason the temp goes that high.
Eventually it will trip given the environ temperatures goes high or your load.
Hope that helps.