Why in poker, K is 13, Q is 12, and J is 11.

Hello.

Because in general.

The size of the card is 23456789 10 J Q K A

But there is no 1. A is the first in ABCD. Just replace 1.

And JQK is larger than 10 in turn. So 11 12 13 said.

Some gameplay methods are slightly different from JQK.

Spring, summer, autumn and winter. Said above.