Grab a beach towel. A blissful summer is expected to follow San Diego’s cool, drab spring.

A cold, drab spring gave way to a warm, sunny start to summer Wednesday across San Diego County, conditions that are likely to dominate until fall, the National Weather Service said.

The most active part of the northern jet stream is expected to migrate back to Alaska and Canada and mostly stay there, rather than continually dipping south and putting the big chill on San Diego.

Forecasters said the pattern change will gradually begin to take root starting late this weekend, after the county experiences unseasonably cool weather on Thursday and Friday.

San Diego will hit 67 on Thursday and 68 on Friday. The seasonal high is 72.

“The water is still cold at the coast, but things will warm up as we get more days of sunshine,” said Alex Tardy, a weather service forecaster. “It looks like we’ll have a pretty normal summer. Things also will heat up inland, and we expect the monsoon to return.”

San Diego typically experiences a lot of cloudy days in January and February. The weather is often more moderate in March and April. That’s followed by lots of cloudiness at the coast in May and June.

But this year has been different. San Diego International Airport did not experience a single fully clear and sunny day from Feb. 15 to June 20. May was especially gray. Forecasters categorized 20 days of the month as cloudy. That means the sky was completely, or nearly completely, overcast.

San Diego also has been comparatively cold. The city is in the midst of its eighth consecutive month of below-average temperatures, the weather service said. The city could break that streak in July if the pattern change unfolds as forecast.

Scientists say that an El Niño has developed in the equatorial Pacific, producing unusually warm waters in that region. It’s possible that the system will turn Southern California waters warmer than normal late this year.