There's only a few days left to get your studded tires removed in Washington. The deadline is March 31st. And while you can keep your studded tires on longer in Idaho, you can't drive into Washington with them on (unless you want a ticket, that is). The fine if you get caught is $124.
In Idaho you have another month, until April 30th, to get your studs off. Over here, fines are $57 for driving with studded tires after the deadline.