milleri - on the verge of sunburn
 

Do you think it will handle these light levels?
Full sun from 10:00 to 20:00.
Day temps have been cool for the season, around 25ºC (77 F) with a forecast of an increase to 35ºC (95 F). The humidity not so low, between 40 and 50%.

Night temps around 12ºC (53 F) and HR 90%.

This more or less mimics the habitat but my concern, together with the light levels, is that the plant should have new growths by now.

https://i.postimg.cc/nXcZwk4T/20200615-191041.jpg

https://i.postimg.cc/ykNsLjXj/20200615-191053.jpg

https://i.postimg.cc/hXknPBFZ/20200615-191103.jpg

https://i.postimg.cc/bZD8hv52/20200615-191124.jpg

https://i.postimg.cc/R69zKLZc/20200615-191138.jpg

https://i.postimg.cc/Dm9PgpTk/20200615-191149.jpg

https://i.postimg.cc/s1QJ5db4/20200615-191226.jpg

https://i.postimg.cc/JtGpKBHJ/20200615-191239.jpg

https://i.postimg.cc/YG2stnSy/20200615-191254.jpg

How long have you had it? The leaves look great. How much are you watering? In habitat they usually have grass growing over them in summer; I would not give your plant more light, and it would be fine with a little less for a safety margin on hot days to come.

I got it almost 2 years ago...it never bloomed.
I always water it before night fall, when temps are below 14ºC (57 F) I mist the medium to mimic the night dew. The actual frequency is every two days. With hot weather, everyday.

Maybe more water. The leaves are wrinkled. Do you fertilize?

Yes, weakly with alternate waterings.

Consider fertilizing more. Your temperatures and light are good enough that nitrogen may be the limiting factor for growth. A lot of semi-desert and desert plants live with cyanobacteria that fix nitrogen. I don't know whether orchids do.

Finally the expected new growth is already visible...hopefully, it will be on time for possible first blooms under my care.

https://i.postimg.cc/6THBc4jy/20200728-201724.jpg

https://i.postimg.cc/SJ3kFFp4/20200728-201740.jpg

https://i.postimg.cc/3ddYcrV9/20200728-201806.jpg

The growth on the previous post died... last summer we had really hot strong winds. I was on vacations and I found this milleri and also my briegeri with new growths broken and dry.

But now I have 3 new growths. Two of them appeared oddly last december and I noticed today a third one which was not visible two days ago. As this plant was bought from a brasilian vendor at a show, I always suspected this plant had its seasons switched. But with new growths appearing now, maybe it got it right.
Let's see ig I'll get my first blooms this summer.:)

https://i.postimg.cc/ykvC6xjh/20210307-162122.jpg

https://i.postimg.cc/k2Hr8HkB/20210307-162140.jpg

Looks like you've backed off on the light?

Now it gets more sun hours than before (I moved to another house) but now I am a little bit more cautious about light levels. Maybe back off a little in summer. In habitat, in the hottest season, there's not as much sun as in the cool season. This means full sun in witer and bright indirect light in summer.