Why is California so dry during the summer? It's all about pressure

VERDOORN EXPLAINS WHY IT’S BEEN SO HOT AND DRY. WELL, IF YOU EVER ASKED YOURSELF THAT QUESTION OF WHY IT GETS SO HOT AND WHY OUR SUMMERS ARE SO DRY, WELL, THE ANSWER IS SIMPLY PRESSURE. HIGH PRESSURE THAT SITS OUT IN THE EASTERN PACIFIC. THE NORTH PACIFIC HIGH IS LOCATED BETWEEN HAWAII AND CALIFORNIA, AND THERE IT SITS IN THE EASTERN PACIFIC AIR CIRCULATES AROUND IN A CLOCKWISE MANNER. AND WHAT THIS DOES IS THIS ACTUALLY HELP TO STEER THE JET STREAM. THE POLAR JET STREAM, WHICH IS A RIVER OF AIR THAT OUR STORMS RIDE ALONG IN. AND WE NEED THAT TO GET OUR RAIN HERE IN CALIFORNIA. NOW, DURING THE WINTER MONTHS, WE HAVE THE HIGH PRESSURE SYSTEM MOVE TO THE SOUTH THAT ALLOWS THE RAIN TO COME INTO CALIFORNIA, AND THAT’S WHEN WE GET THE BULK OF OUR RAIN IS DURING THE WINTER MONTHS, WHEN THE HIGH PRESSURE IS MOVED CLOSER TO THE EQUATOR. BUT DURING THE SUMMER MONTHS, THAT AREA OF HIGH PRESSURE, WELL, IT MOVES MORE TOWARDS THE POLES. AND SO AS IT MOVES NORTH, THE JET STREAM MOVES WITH IT. AND SO THE WET WEATHER GOES FROM THE PACIFIC NORTHWEST ON INTO CANADA. AND WE CAN HAVE SOME VERY LONG, DRY SUMMERS WITHOUT ANY SIGNIFICANT RAINFALL IN SOME CASES UP TO SIX MONTHS IN FACT, WE CAN HAVE SOME TIMES WHERE THIS AREA OF HIGH PRESSURE SITS OUT HERE IN THE EASTERN PACIFIC FOR MORE THAN SIX MONTHS. AND THAT’S WHEN WE HAVE OUR DRY SPELLS THAT LAST. AND WE GET THE DROUGHTS THAT OCCUR HERE IN CALIFORNIA. NOW, WHEN THAT AREA OF HIGH PRESSURE MOVES A LITTLE BIT CLOSER TO THE COAST OF CALIFORNIA, YOU CAN SEE THE AIR COMING FROM THE NORTH THAT SETS UP FOR A HOT, DRY NORTH WIND. AND THAT’S SOMETHING WE DO NOT LIKE TO SEE, ESPECIALLY DURING THE SUMMER MONTHS WHEN EVERYTHING IS SO DRY FROM THE LACK OF RAIN THAT CAN CAUSE SOME PROBLEMS AND CREATES A MUCH HIGHER FIRE DANGER. NOW, AS THIS STARTS TO MOVE OFF TOWARDS THE WEST, IT OPENS THE DOOR FOR ANOTHER AREA OF HIGH PRESSURE. AND THIS IS THE FOUR CORNERS HIGH. THIS IS ASSOCIATED WITH THE MONSOON WHERE IT SCOOPS UP THE WARM, MOIST AIR FROM THE GULF OF CALIFORNIA AND THE GULF OF MEXICO, BRINGING THUNDERSTORMS TO THE SOUTHWESTERN STATES. NOW, AS THE NORTH PACIFIC HIGH MOVES WEST, THIS AREA OF HIGH PRESSURE OVER THE FOUR CORNERS WILL ALSO MOVE WEST, BRINGING THE MONSOON TO CALIFORNIA. AND THAT’S WHEN WE CAN HAVE OUTBREAKS OF THUNDERSTORMS. IN FACT, THOUSANDS OF LIGHTNING STRIKES, WHICH CAN CAUSE SOME FIRES AND SOME VERY REMOTE LOCATIONS, MAKING IT VERY DIFFICULT FOR FIREFIGHTERS TO FIGHT. SO AGAIN, IF YOU EVER ASK YOUR QUESTION, WHY DO WE HAVE THESE LO

California is known for its hot and dry summers. The rainy season is usually over by May, and skies can stay relatively dry through October, which can make for up to six months without any significant rain.Why is California so dry during the summer? Well, it’s all about pressure. There is a semi-permanent area of high pressure that resides in the northeastern portion of the Pacific Ocean. The North Pacific High helps to steer the Polar Jet Stream, which is a river of air that carries storms into North America. During the winter months, the North Pacific High shifts south, allowing the jet stream to drop over Northern California, bringing much-needed moisture to the state.During the summer months, the North Pacific High shifts north, steering the jet stream along with all of the rain chances into the Pacific Northwest and Canada.There are times when the North Pacific High does not move far enough south during the winter months, making rain chances sparse, leading California into drought.If the North Pacific High moves closer to California, it can lead to a hot, dry north wind, increasing fire danger in the state. If the North Pacific High moves to the west, it can lead to the monsoon entering the state from the southwestern states. This brings numerous thunderstorms with thousands of lightning strikes, which increases the fire danger by starting fires in remote areas of the mountains.So when the long, hot summer arrives in California, and the fire danger goes up, remember, it is all because of pressure.This story was produced as part of our Wildfire Ready special. See more resources with our 2024 guide for how to prepare for wildfires in California

Why is California so dry during the summer? Well, it’s all about pressure.

There is a semi-permanent area of high pressure that resides in the northeastern portion of the Pacific Ocean.

The North Pacific High helps to steer the Polar Jet Stream, which is a river of air that carries storms into North America.

During the winter months, the North Pacific High shifts south, allowing the jet stream to drop over Northern California, bringing much-needed moisture to the state.

During the summer months, the North Pacific High shifts north, steering the jet stream along with all of the rain chances into the Pacific Northwest and Canada.

There are times when the North Pacific High does not move far enough south during the winter months, making rain chances sparse, leading California into drought.

If the North Pacific High moves closer to California, it can lead to a hot, dry north wind, increasing fire danger in the state. If the North Pacific High moves to the west, it can lead to the monsoon entering the state from the southwestern states. This brings numerous thunderstorms with thousands of lightning strikes, which increases the fire danger by starting fires in remote areas of the mountains.

So when the long, hot summer arrives in California, and the fire danger goes up, remember, it is all because of pressure.

This story was produced as part of our Wildfire Ready special. See more resources with our 2024 guide for how to prepare for wildfires in California

Why is California so dry during the summer? It's all about pressure

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