The drought is linked to the fact that 2014 is on course to be the warmest year on record, according to the National Oceanic and Atmospheric Administration’s Climate Prediction Center.

The forecast of a warm winter comes after a summer of record-breaking temperatures, as well as a late-season heat wave that made drought conditions worse and increased the rate of evapotranspiration, or the transfer of water from soil and other surfaces to the atmosphere by evaporation and by transpiration from plants.

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Why such a widespread problem?

Around a third of California’s water supply comes from meltwater runoff from the snowpack, levels of which were considerably less than average this year. Consequently the 154 largest state reservoirs are operating at just 36% of storage capacity, holding around 13.5 million acre feet of water.

Weather patterns also conspired to keep California dry last year, with a persistent ridge of high pressure over the Pacific keeping storms from hitting land.

The latest update from the U.S. Drought Monitor places the whole of California in some kind of drought category, in accordance with government-issued reports from the last three months. Over half of the state is suffering an “exceptional drought”, which is the most severe category.

Reports claim that southern California has a small chance of a wetter-than-average winter, but central and northern areas have equal chances of seeing average, below-average and above-average precipitation over the months of November, December and January.

California drought: Prospects for improvement

California sees the majority of its precipitation in winter, but the existing drought conditions are so severe that prospects of improvement are slim.

“Complete drought recovery in California this winter is highly unlikely,” said Mike Halpert, acting director of NOAA’s Climate Prediction Center. “While we’re predicting at least a 2 in 3 chance that winter precipitation will be near or above normal throughout the state, with such widespread, extreme deficits, recovery will be slow.”

One important factor is the development of the El Niño weather pattern. There is a 67% chance that the system will form this year, but if it does arrive it is not expected to bring enough precipitation to end drought conditions.