About 80 million packages are being delivered to U.S. households each day.

WARRENDALE, Pa. (KDKA) — On Wednesday, 18-wheelers wrapped around the post office in Warrendale.

Truck drivers and mail carriers are under the intense pressure of meeting the 50 percent increase in demand for online orders this holiday season.

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“They are still holding up in the mid-90s, which is 94 to 95 percent. That is exceptional given the surge of millions of packages a day,” said Shipmatrix president Satish Jindel.

An exceptional on-time rate considering 80 million packages are being delivered to U.S. households each day. And because of the demand, roughly two million packages will experience delays of two or more days, according to Shindel.

But with winter storms bearing down on the U.S. one week before Christmas, Shindel said, “If they were expecting it on this Thursday or Friday, they may get it Saturday, Sunday or Monday.”

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Whether or not your presents make it under the tree by Christmas depends on the weather next week, Shindel told KDKA. And should winter weather put a freeze on deliveries, online shoppers could experience even more delays as mail carriers plan on prioritizing coronavirus vaccines and tests.

“That is of great importance to our country and they will not let that slip,” Shindel said.

On Wednesday, a FedEx spokesperson released a statement, saying:

We have a team of 15 meteorologists monitoring conditions 24/7, and about 185 specialists coordinate the movement of millions of shipments on thousands of flights and trucks every day. For vaccine shipments in the U.S., we are using our SenseAware ID monitoring technology and our Priority Alert service to track their movement throughout the FedEx Express network. This, and the strength and flexibility of the FedEx Express air and ground network, allows us to quickly implement contingency plans to help mitigate any potential delays.

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Meanwhile, UPS released the following statement:

UPS recently opened a new healthcare command center at Worldport, our global air hub in Louisville, Ky. The command center watches every package of COVID-19 vaccines from origin to destination, and can step in with contingency plans should it appear that a package may be delayed.