If you live east of the Rockies you probably don’t see anything strange with rain this time of year. But here in the Central Valley of California summer rain
isused to be an oxymoron.
In non-drought years (a whole ‘nother story) we would get plenty of precipitation, but 90% of it came during November through March, and 99% of it came between October and May. Back east dams are for flood control and hydroelectric power. We use them for that too, but they are also essential for irrigating crops and residential use as well.
Before the white man came the Central Valley was a mosquito filled swamp in the spring and a desert in the summer. The Native Americans would come down to hunt or gather acorns and then skedaddle back into the hills (proving that while they may have been ignorant savages they were no dummies.) When the white man arrived he started building dams and irrigation canals so he could farm during the dry summer months.
It’s summer, so why is it raining outside my house right now?
The answer is global warming. Yeah, yeah, I know the climate change deniers would say just the opposite, but they’re idiots. Let me give you a little geography lesson.
The Central Valley is separated from the Pacific coast and the San Francisco Bay by a low mountain range. If you’ve never been out here but you watch shows like Baywatch you probably think the Pacific coast is nothing but a series of sunny beaches filled with surfers and bikini-clad babes. That impression provides lots of entertainment for the locals when we get to watch scantily-clad tourists turning blue from the freezing winds.
Remember that alleged quote from Mark Twain?:
“The coldest winter I ever spent was the summer I spent in San Francisco.”
Mr. Clemens never actually said it but he could of. That’s because the prevailing winds here come from the northwest – from the Gulf of Alaska. Not only that but the water is pretty cold too.
When we move into summer the land heats up faster than the water. This warms the air over the land which causes it to rise. When the warm air rises it is replaced with cold moist air coming in from over the ocean.
That’s why most places along the west coast (like San Francisco and Monterey) are cold and overcast this time of year, with chilly gale-force winds blowing in from over the water. (Tourist tip: By late summer/early fall the water is warmer so the temperature differential is smaller and the coastal weather is much nicer.)
Normally the coastal range blocks that cold moist air from the Central Valley, and we enjoy sunny, dry days in the low nineties. But because of global warming we have been getting unusually high temperatures early in the year. (Last week it went over 100 degrees for several days in a row.)
This heats the air and causes it to rise which literally pulls the cold, moist air in over the coastal range. Once that cold mist air gets here it warms up, rises, and then cools. This causes the moisture to condense and turn into rain drops.
And that is why it is raining in the Central Valley again for the umpteenth time this month.
BTW – Usually by this time of year most of the wild grasses and weeds have stopped growing and turned brown. Farmers, homeowners and road & fire crews have cut them down or back to prevent fires. These late season rains will have them growing bigger and/or re-growing in places they were already cut down. August and September should be a real hot time around here.
Watch this climate change ad from Greenpeace (ironically, it’s via Hot Air):