Yes it is safe to delete these files. You should clean out these temp files at least weekly.
I recently had a machine that was very slow. I opened the temp file folder and found more than 26,000 temp files. It took about 45 minutes to delete all of them. Afterward the machine ran at normal speed.
This should be a part of regular maintenance on a computer. It can help to keep your machine running properly.
Good Luck.