Summary for California and Nevada

El Niño Advisory: Positive equatorial sea surface temperature (SST) anomalies continue across most of the Pacific Ocean. There is a greater than 90% chance that El Niño will continue through Northern Hemisphere fall 2015, and around an 85% chance it will last through the 2015-16 winter.

California and Nevada

Temperature

August

Only western and coastal areas of California are above normal for temperature with most of the other three states being slightly to moderately below normal.

September

Temperatures for much of the four state area return to near normal. Much of eastern Nevada and eastern Oregon should be cooler than normal.

October

Warmer than normal across the entire four state region with temperatures in the mountainous areas at close to 1 degree C (1.8 degree F) above normal.

November

Warmer than normal across the entire four state region with temperatures in the mountainous areas at close to up to 0.4 degree C (0.7 degree F) above normal.

December

Warmer than normal across the entire four state region with temperatures in the mountainous areas at close to up to 0.4 degree C (0.7 degree F) above normal and with small and isolated areas along the coast being slightly below normal.

January

Near normal to slightly normal across the entire four state region with temperatures with slightly warmer than normal conditions in southern California and far southern Nevada.

Precipitation

August

Much of California and the southern half of Nevada should be considerably wetter than normal however long term normal precipitation for the month is very low for the Central Valley. Mountainous areas have slightly greater rainfall than the month of September so the positive anomaly is a welcome outlook. Much of the coastal ranges of Oregon and Washington remain slightly drier than normal with much of the rest of both states being near normal to only slightly drier or along the coast slightly wetter than normal.

September

Much of California and the southern half of Nevada should be wetter than normal however long term normal precipitation for the month is very low for the Central Valley. Oregon and Washington remain drier than normal but only slightly while northwest Washington should be slightly above average.

October

Near normal throughout the region but slightly wetter than normal south of Bakersfield and across southern Nevada while much of the rest of the state is should be close to normal for this historical month for the onset of the wetter season. In Washington and Oregon near normal to slightly wetter than normal conditions should prevail.

November

Most of California and Nevada should be slightly wetter than normal but only slightly and this is a rainy season month. The southern half of the two state area in contrast could be moderately wetter than the long-term average although in the southern-most part of California this is a very dry month historically. Washington and Oregon should be near normal.

December

The northern third of the California and Nevada should be slightly to moderately drier than normal while the central and southern parts of both states should be close to normal and just the southern third of California should be only slightly wetter than normal. In Washington and Oregon slightly drier than normal conditions are forecast with slightly wetter conditions in the mountains of central Oregon and in the Cascades to the east of Seattle.

January

The northern third of the California and Nevada should be slightly to moderately drier than normal while the central and southern parts of both states should be close to normal and just the southern third of California should be only slightly wetter than normal. In Washington and Oregon slightly drier than normal conditions are forecast with slightly wetter conditions in the mountains of central Oregon and in the Cascades to the east of Seattle.

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