Oil prices tumble 20% in May - the biggest monthly drop since 2020. Here's what's next.

By Isabel Wang and Myra P. Saefong

Angst on Wall Street about being caught off-guard if the U.S.-Iran war ends quickly sent global oil prices tumbling more than 20% in May. Both the U.S. and global benchmarks are now on pace for their biggest monthly swoon since the start of the onset of the COVID-19 crisis more than six years ago.

Brent crude saw its July contract (BRN00) (BRNN26) fall nearly 20% in May to $90.71 a barrel on Friday, the last trading day of the month and for the front-month contract. The international benchmark was on track for its largest one-month net and percentage decline since March 2020, when the pandemic triggered a historic demand shock that crashed global oil markets.

West Texas Intermediate crude for July contract (CL.1) (CLN26) has fallen 17% this month to $86.83 a barrel, also capping its worst month since early 2020 and snapping a four-month winning streak, according to FactSet data.

See: Oil prices slide as Trump says the U.S. is close to an Iran deal