Why doesn't our summer weather usually begin until after July 4th...instead of near the Solstice?
The answer is related to our northerly latitude and our coastal location...on the west coast! The Pacific High which blocks incoming disturbances and typically brings a drier northerly flow takes time to build northward. The farther your location to the north...the later the Pacific High provides protection. Although the jet stream weakens and retreats northward by late spring and summer, our far northerly latitude exposes us to more disturbances carried by the jet. We're as far north as Bemidji Minnesota and St. John's Newfoundland! And water temperatures are slower to rise than air temperatures. Given the frequent motion of air over the Pacific on it's way inland, that slow warming also is a major factor.