January is supposed to be one of the wetter months, normally generating 4.5 inches of rain.
CNN  — 

With sunny skies in the forecast for Saturday, San Francisco is on the verge of a recording-setting month – a January with absolutely no rain.

This isn’t just rare, it’s hasn’t happened in the region’s recorded weather history, dating back to the Gold Rush in 1850.

San Francisco is not alone in its rain-free streak. Oakland and Sacramento have yet to have any measurable rainfall in 2015. These are the extremes, but almost all of northern California will finish the month well below the average precipitation for the normally wet month of January.

This NOAA image shows the last month of rainfall levels across the state. There is a noticeable hole over the Bay Area, extending inland.

As most of California grapples with extreme drought conditions, forecasters had anticipated a wetter-than-average month in January. December was especially wet with 11.7 inches of rain. Then January swept through and essentially erased all the progress made late last year.

Most of California is under extreme or exceptional drought conditions according to the U.S. Drought Monitor.

San Francisco averages 4.5 inches of rain in January, according to the National Weather Service. The previous minimum record was set last year when only 0.06 inches fell in January, and 2013 saw less than half an inch. The last three years all rank in the lowest five January rainfalls on record.

The dry weather is impacting the normally lucrative ski season near Lake Tahoe, on the California-Nevada border.

The Donner Ski Ranch is closed this week. A post on its website blames it on “the warm, snow-free weather impacting the Sierra Nevada” mountains.

Owner Janet Tuttle says the resort got a tiny bit of snow this week “but not enough to make a difference, really.” Tutttle went on to say the resort will just wait for the “next major storm to come through before re-opening”.

Several other ski resorts are closed or operating only some runs.

According to the U.S. Drought Monitor, California “led the nation with 78 percent coverage of extreme to exceptional drought.”

CNN’s Dan Simon contributed to this report.