High-pressure ridge blocking storms from reaching Calif. can be seen from space

A satellite image of the West Coast from NOAA shows the high-pressure ridge blocking storms from reaching California. A satellite image of the West Coast from NOAA shows the high-pressure ridge blocking storms from reaching California. Photo: NOAA UW-Madison Photo: NOAA UW-Madison Image 1 of / 24 Caption Close High-pressure ridge blocking storms from reaching Calif. can be seen from space 1 / 24 Back to Gallery

It's February and the San Francisco Bay Area hasn't seen a drop of rain all month.

Predicting the weather beyond a week with accuracy is difficult, but there's a chance the region may not see a significant storm the entire month, something that hasn't happened since February 1864, according to data from the National Weather Service.

How could it be so dry at a time that's historically the wettest of the year? A high-pressure ridge stretched across the eastern Pacific Ocean is steering storm activity to the Pacific Northwest and keeping California dry.

"If you look at weather stories about Seattle right now, they’re getting hammered with storm after storm," said Jan Null, a consulting meteorologist with Golden Gate Weather Services. "The storms are going up over the top of the ridge into the Northwest, but not dipping down over California."

ALSO: Why temperatures in the Bay Area are unseasonably warm on Tuesday

An image from a NOAA satellite helps put the ridge of high pressure into perspective, showing completely clear skies over California as clouds hover over the edge of the eastern Pacific Ocean and the Pacific Northwest. (See image above.)

NOAA's Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison posted the image on Twitter, writing, "Can you spot the high pressure???"

NBC Bay Area meteorologist Rob Mayeda shared it, writing, "Beautiful view of an ugly pattern for rain chances here via the @UWCIMSS team."

Amid the prolonged dry spell, rainfall totals for the season are running well below normal. The National Weather Service measures totals using the "water year," running from October to September, and nearly all Bay Area locations are running a deficit for the year.

The rain gauge in San Francisco on average measures 14.99 inches between Oct. 1 and Feb. 10, but this year, it has received just 8.83 inches, or 59% of normal. The Santa Rosa Airport is at 69% of normal and San Jose 43% of normal.

"Until we get some rain, those percentages against normal to date are going to keep falling," said Null.

There's a slight chance of rain in the North Bay on Saturday night into Sunday morning as the southern edge of a storm hitting the Pacific Northwest may deliver sprinkles.

"This has been a theme all year," said Scott Rowe, a meteorologist with the National Weather Service's Bay Area office. "Their umbrellas in the Northwest have been put to good use with storm after storm, and we find ourselves at the tail end of these storms."

The system in the Northwest will weaken the high-pressure ridge over the weekend, but it's expected to rebuild, keeping the region dry next week.

The high pressure is also contributing to unusually high temperatures on Tuesday as many locations around the Bay Area soared into the 70s, and even the 80s, in the afternoon. The mercury is expected to drop Wednesday as wind patterns shift; temperatures Wednesday afternoon will likely be 5 to 10 degrees cooler than they were on Tuesday.

Amy Graff is a digital editor with SFGATE. Email her: agraff@sfgate.com.