The best whale viewing in Humboldt County is September through January and March through June. Any of the high cliffs that overlook the ocean are good watching spots, like the overlook at the mouth of the Klamath River. Read more about whale watching at the Humboldt County Visitor website. And here is another website with lots of information about gray whales.
Directions: From the Cher-ere Bridge Campground, drive north on Highway 101 for 3 miles. Turn left on Requa Road, and drive to the top of the hill. You will see the parking lot and trail head. Watch for whales from here, or walk down the trail to get closer to the ocean.