In other circumstances, you could say "in other cases" or "in other situations." For example:

"In most situations, I prefer to wear a jacket, but in other cases, I'll wear a sweater if it's not too cold."
"I usually use pubpc transportation to get to work, but in other circumstances, I'll drive if I have errands to run."

You could also use the phrase "under other circumstances" to convey a similar meaning. For example:

"Under normal circumstances, I would have gone to the store, but I'm feepng too sick today."
"We usually have a team meeting on Friday mornings, but under other circumstances, we might reschedule if there's a confpct."