special circumstances
Refers to exceptional or unusual conditions that affect a situation, often used in formal or explanatory contexts.
Due to special circumstances, we will be closed today.
Because this area has special circumstances, special measures are needed.
事情 means 'circumstances' or 'reasons' in general, while 特殊事情 specifically refers to exceptional or unusual circumstances.
Compound of 特殊 (とくしゅ, 'special') and 事情 (じじょう, 'circumstances').