You really must not allow this to happen. Fix this cooling problem or it will only cause more problems.
Most people only do monthly parity checks. Some even do less frequently for servers that aren't always on. Parity checks aren't required to maintain parity, they are just checks. Parity is always updated in realtime.
You didn't answer this question:
Some people mistakenly think parity is the most important disk. In order to rebuild a missing disk, parity PLUS ALL remaining disks must be reliably read in order for the parity calculation to get the data to rebuild. Parity by itself can't recover anything. Also, parity doesn't actually contain any of your data, unlike the data disks. So arguably parity is the least important disk.
Have you ever replaced a disk before? Do you know how? Please ask for more advice if you are unsure.