I guess we would have to include Olympic NP in the itin since Summer would be very different from the rainy (and very cold too) March.
I counted a grand total of 8 hours of sun ray, included those from the thick cloud, in our 9 day total trip in the region between Portland, Seattle and Vancouver, covered the whole Olympic Peninsula, Oregon Coastal, and Vancouver.
But, the record was one winter we drove pass our hotel at Vancouver - I think it is Westin or Sheraton, at the Yacht Club, just before the Lion Gate bridge, 3 times and not seeing its sign at the road side due to very very dense fog. Unbelievable.