Here's why your Starbucks order might take longer today

• On Red Cup Day, Starbucks fans receive a free reusable red cup with purchase of a holiday drink.
• The event, dubbed Red Cup Day, is one of the busiest days of the year for the chain.

Starbucks customers might face longer than usual wait times for their daily caffeine fix – and potentially cafe shutdowns – as baristas plan to strike on November 16, Red Cup Day.

During the annual event, Starbucks customers receive a free reusable 16-ounce red cup when they purchase a fall or holiday beverage. It's one of the busiest days of the year at Starbucks as fans flock to stores to collect this year's limited-edition cup, described by the chain this year as a "whimsical mod design."

Starbucks Workers United, the union representing more than 360 stores that have voted to unionize, said workers are walking out for the second year in a row on Red Cup Day. They are protesting what they say is the chain's inability to staff appropriately during big promotional events.

The planned walkout comes as negotiations between the union and Starbucks have stalled. Both sides have accused each other of being unwilling to negotiate a contract.

The union is calling the walk-out Red Cup Rebellion. Baristas are expected to walk off the job at 9 am local time. Rallies are planned in various cities, including New York, the union said. On Wednesday, the union said about 30 stores launched a surprise strike as well. The 'surprise strikers' will remain out of work on Thursday, the union said.

Last year, Starbucks workers from over 100 stores walked off the job on Red Cup Day. The union said they expect twice the number of stores to participate this year with a potential for hundreds of stores to shut down. Starbucks has about 38,000 stores.

The union is also asking Starbucks to turn off mobile orders for the promotional event.

"Starbucks workers can't keep working with such short staffing," said Neha Cremin, a barista in Oklahoma City. "At my store, we're expected to make drive-thru orders, walk-up orders, mobile orders, and delivery orders. This is difficult enough to manage with a fully-staffed floor, but we're often expected to manage all these things with only three workers."

When asked if they plan to increase staffing on Red Cup Day, a Starbucks representative told Insider: "Our store schedules are thoughtfully based on anticipated and historical trends, and created three weeks in advance with our partners' availability and preferences at the forefront."

Mobile ordering decisions are made at the store level. Starbucks said store leaders monitor access to mobile ordering and can adjust it based on things like staffing and customer traffic.

Are you a Starbucks worker with insight to share? Got a tip? Contact this reporter via email at nluna@insider.com or via Signal encrypted at 714-875-6218.