"Exceptional circumstances" refers to unusual or uncommon events or situations that are out of the ordinary. It means that something very unique or special has occurred, generally requiring special consideration or response. Full definition
You can exit from the scheme only in case of exceptional circumstances such as death of beneficiary or a terminal disease. (policybazaar.com)
There are also cases when there are exceptional circumstances where one parent has sole parental responsibility and has all of the decision making ability. (familymaritallaw.com)
In other words, the power was needed for exceptional circumstances. (bbc.co.uk)