MAJOR ARTERY BETWEEN FREMONT AND SUNOL HAVE BEEN CLOSED SINCE MONDAY. >>> WE'VE SEEN A LOT OF RAIN IN RECENT WEEKS, BUT THIS WINTER IS ALSO GIVING US SOMETHING WE HAVEN'T SEEN MUCH OF THIS CENTURY, BUT BEFORE WE ABOUT THIS YEAR, LET'S FLASH BACK TO LAST YEAR. >> WE WERE COMING HOME ON 280 AND YOU COULD HARDLY SEE. >> THE WINTER OF 2022/'23 BROUGHT A LONG PARADE OF STORMS THAT TOOK TURNS BATTERING PARTS OF NORTHERN CALIFORNIA AND WE SAW ABOVE AVERAGE RAINFALL. IT WAS ENOUGH TO END THE DROUGHTS AND FILL MOST OF OUR RESERVOIRS. SO HOW IS THIS YEAR LOOKING? WELL, IT'S LOOKING PERFECTLY AVERAGE. THAT'S RIGHT. WE'RE CURRENTLY RIGHT ON TRACK FOR AVERAGE RAINFALL IN NORTHERN CALIFORNIA, BELIEVE IT OR NOT. THIS IS KIND OF UNUSUAL. WILSON WALKER JOINS US LIVE TO EXPLAIN WHY HAVING THIS AVERAGE WINTER IS ANYTHING BUT NORMAL. HEY, WILSON. >> Reporter: GOOD EVENING. EARLIER TODAY A COLLEAGUE OF OURS REMARKED THEY WERE READY FOR THE RAIN TO WIND DOWN AND THEY ADDED THAT THEY UNDERSTOOD THAT THIS WAS A STATISTICALLY AVERAGE WINTER AS WE JUST NOTED, BUT AVERAGE CERTAINLY ISN'T NORMAL ANYMORE. IF YOU TAKE THIS AVERAGE YEAR AND YOU ADD IT TO LAST YEAR'S ABOVE AVERAGE YEAR, WELL, THINGS GET ODDER STILL. >> LIKE SHASTA AND OROVILLE ARE WELL ABOVE THEIR HISTORICAL AVERAGE, BUT THEY AREN'T FULL. THEY COULD BE FULL, BUT THEY CAN'T BE FULL BECAUSE YOU HAVE TO LEAVE SOME SPACE TO MANAGE FLOODS. >> Reporter: WATCHING THE RESERVES STACK UP ACROSS CALIFORNIA, WATER RESEARCHER JEFFREY MOUNT AND THE WINTER OF 2023/2024 QUICKLY BECOMING REMARKABLE IF YOU TAKE THE WIDE ANGLE VIEW. >> PRECIPITATION BACK TO 1950 AND THIS IS THROUGH 2022 AND ONE OF THE REALLY STRIKING THINGS YOU SEE ABOUT THE 21st CENTURY THAT POST 2000 IS HOW MANY DRY YEARS, JUST A LOT OF DRY YEARS. >> THIS IS 2014. THIS IS WHAT WE DO. >> I DON'T KNOW HOW LONG WE CAN GO WITH THIS. >> Reporter: THE DROUGHT THAT STRETCHED FROM 2012 TO 2016 WAS CONSIDERED THE WORST ON RECORD AND ENDED WITH THE SINGLE WETTEST YEAR ON RECORD IN NORTHERN CALIFORNIA IN 2017 AND ALMOST JUST AS QUICKLY THE STATE DESCENDED RIGHT BACK INTO MORE YEARS OF DROUGHT. >> THE REAL FEAR IS WHAT'S NEXT YEAR BRING? WHAT HAPPENS NEXT YEAR? THE SO-CALLED AVERAGE YEAR LIKE WE'RE HAVING NOW IS BECOMING RARER AND RARER. THIS IS A CLIMATE CHANGE SIGNATURE AND THAT IS OUR WET YEARS ARE BECOMING WETTER AND OUR DRY YEARS ARE BECOMING DRYER. THAT'S THE SIGNATURE THAT'S REALLY STARTING TO SHOW UP. >> Reporter: THIS AVERAGE WINTER GETS EVEN MORE NOTABLE WHEN YOU CONSIDER HOW RARE IT IS BECOMING TO HAVE A WET YEAR LIKE LAST YEAR FOLLOWED BY ANYTHING OTHER THAN A DRY ONE. >> WE'RE ALMOST A QUARTER DONE WITH THE 21st CENTURY AND WE'VE ONLY HAD TWO PAIRS OF YEARS WHERE WE'VE HAD WET BACK-TO-BACK YEARS, THIS ONE AND BACK IN 2004 AND 2005. >> Reporter: CALIFORNIA, A STATE BUILT ON THE WHIMS OF VARIABLE WEATHER, IS ONLY SEEING MORE OF IT AS EXTREMES BECOME THE NORM AND AVERAGE BECOMES INCREASINGLY UNCOMMON. >> BUT WHAT'S HAPPENING IS THAT THAT VARIABILITY SEEMS TO BE INCREASING, THAT THE DRIES ARE GETTING DRIER AND THE WETS ARE GETTING WETTER AND THAT'S OUR HUGE CHALLENGE FOR MANAGING IN THE FUTURE. >> Reporter: WE SHOULD ADD WE'RE TALKING SPECIFICALLY ABOUT NORTHERN CALIFORNIA. SOUTHERN CALIFORNIA HAS HAD A HUGE WATER YEAR, BUT IMPORTANT TO REMEMBER 75% OF ALL PRECIPITATION THAT FALLS IN CALIFORNIA FALLS NORTH OF SACRAMENTO WHERE ALL OF OUR STORAGE IS. EVEN IF 75% OF THE PEOPLE WHO USE IT LIVED SOUTH OF SACRAMENTO, THAT, OF COURSE, WOULD BE THE REAL TRICK OF CALIFORNIA WATER THERE. IT'S AN INTERESTING THING, RYAN, THAT AVERAGE IS SO OUT OF TH
