If your thermometer is accurate, this is OK. It is about the upper limit of OK for many species. IMO and IME, if you can keep the max temp of about 82 degree, it is better. Other people may disagree. In the summer, my tank go up to 84 daily. It is doing fine with clams and SPS growing very fast.
to be safe I would recomend 82.. 84 is the limit imo
82 allows for a margin of error. Also when running that close to the edge I would some type of light's out temperature protection..
On my systems if temp > or = to 84.1 all lights go out.. This has happened a few times and I am happy it did..
If you are going to ride the upper limit you need to be careful.
I have read studies on natural reefs where water temp has been measured at > 90. These temps were not constant however. I regularly run my tank at 80-82 with temp as high as 86 in summer months without any apparent adverse effect.