New Jersey Transit and Amtrak rail service was severely disrupted this week, leaving some commuters stranded for hours on the hottest days of the year.

Extreme heat coupled with strained infrastructure, malfunctions and mechanical problems on Amtrak and New Jersey Transit brought agony and massive delays for tens of thousands of commuters throughout the Northeast this week.

Rail service between New Jersey and New York’s Penn Station was suspended Thursday before the evening commute and again on Friday morning, with New Jersey Transit citing “AMTRAK overhead wire issues.”

While the root cause of the disruptions is still being investigated, they hit during some of the hottest days of the year so far, lengthening commutes amid an early-summer heat wave.