Current Drought Conditions 

Although winter is typically considered the wet season for California and 

Nevada, below-normal precipitation has many in the region once again thinking 

about drought. Over the past two months, abnormally dry (D0) conditions 

have expanded across the southern and Sierra regions of California and most 

of Nevada according to the U.S. Drought Monitor (Fig. 1). Moderate drought 

(D1) conditions have also expanded in Southern California and in the Southern 

Central Valley, in addition to the lingering moderate-severe drought near the 

south-central coast. As of January 30, 30% of California-Nevada is in moderatesevere drought and 54% is abnormally dry.

CALIFORNIANEVADA 

DROUGHT 

OUTLOOK 

JANUARY 2018

National Integrated Drought 

Information System

Drought.gov

Fig 1. U.S. Drought Monitor for January 

30. Source: droughtmonitor.unl.edu

Regional Climate Update

California and Nevada remain dry following a dry 

start to the water year (October 1). Although some 

precipitation has fallen over the region, much of 

Nevada and Southern California have received 

less than 50% of normal precipitation, and parts of 

Northern California have received 70-90% of normal 

(Fig. 2). According to California Department of Water 

Resources, precipitation 8-station index and 5-station 

index measurements in the northern and central 

Sierras are below the 1966-2015 average. Based on 

historical data, the Western Regional Climate Center 

(WRCC) has indicated that much of the region is 

unlikely to reach normal conditions. For example, 

most stations shown only have a 10-30% likelihood 

of reaching their respective mean water year (Oct 

1 - Sept 30) precipitation total (each station starts the 

water year at 50%). 

December and January temperatures have also 

been warmer than normal, with some areas up 

by 6-8°F. These warm temperatures and a lack of 

precipitation have impacted snowpack. NRCS SNOTEL

measurements across the region are reporting snow 

water equivalent (SWE) of less than 25% of median 

for this time of year – including in Sierra Nevada. 

Snowpack levels are also low in eastern Nevada 

(currently <50% of normal SWE), and in the Colorado 

River Basin - which provides water resources to 

Southern California and Nevada. Although storms in 

early January relieved some dryness, soil moisture 

is low across the region and will likely remain low in 

the coming months. Soil moisture percentile values 

in southwestern Nevada are showing conditions that 

are in the driest 5% of historical observations for this 

time of year, and across California there are also large 

swaths that fall within the driest 5-30% in history.Most 

reservoir levels are still above their historical averages 

from last year’s wet winter. Continuing to monitor 

temperature as well as precipitation will be important 

throughout winter to understand how much 

precipitation falls as rain, rather than accumulating 

snowpack, which will impact pre-April snowmelt. 

For more information about NIDIS, visit the U.S. Drought Portal at www.drought.gov

 Fig. 2. (a) Percent of Normal Precipitation (%), 10/1/2017-

1/23/2018. (b) Departure from Normal Temperature (F), 11/25/2017-

1/23/2018. Source: hprcc.unl.edu/maps.php?map=ACISClimateMaps

(a) (b)
Did drought play a role in the recent California 

wildfires? 

Recent wildfires in California, three of them among 

the ten most destructive in the state’s history, 

resulted in mass evacuations, deployed resources, 

destroyed structures, and loss of life. The northern 

California fires ignited during a Diablo wind event, 

preceded by a wet winter/spring, hot summer, and 

dry fall. The southern California fires ignited during 

a Santa Ana wind event following a dry autumn and 

extended dryness linked to the 2012-2017 drought.

 It is still to be determined what role long-term 

drought played in setting up conditions for these 

fires. Wildfire is dependent on ignition sources and 

the availability and type of fuels. The availability 

of vegetation as fuel is affected by the previous 

seasons’ precipitation and drought conditions in 

preceding years. The wet winter of 2017 supported 

vegetation growth across the region, and over the 

summer and fall that vegetation dried out, creating 

more fuels and adding to existing fuels that may 

have remained from previous long-term drought. 

Long-term drought in southern California may 

have had more of an impact on wildfire than in 

northern California, but more studies are needed to 

determine the role of long term drought on these 

wildfires.

Drought & Climate Outlook

The January 2018 Seasonal Outlooks produced by 

NOAA’s Climate Prediction Center (CPC) show equal 

chances of above, below, or normal precipitation for 

northern California and Nevada for February-MarchApril (FMA) and March-April-May (MAM), and increased 

odds of below-normal precipitation (33-50%) for 

the southern portion of the region (Fig. 3). There 

is a 33-50% chance of above-normal temperatures 

over much of the region through spring, with the 

greatest chances centered over southern Nevada 

and southern California. Through April, drought is 

expected to persist in the southern central California 

coast and near the southern California-Arizona border, 

with potential drought development in western 

central California. These outlooks reflect the typical 

wintertime La Niña-related circulation patterns (i.e. 

northern displaced polar jet stream and mean storm 

track). 

La Niña conditions continued through the winter, with 

below-average equatorial sea surface temperatures 

(SSTs) across the central and eastern Pacific Ocean. 

NOAA’s ENSO alert system status is a La Niña advisory 

with conditions favored to continue through the 

Northern Hemisphere winter with a transition to 

ENSO-neutral expected during the spring. The official 

probabilistic ENSO forecast as of early-January, 

combining observational and predictive information 

with human judgement, shows La Niña conditions 

have a high chance of continuing through early 

spring (~60-85%). The chances of neutral conditions 

increases in spring into summer. The multi-model 

averages also predict La Niña to persist into spring 

before this transition.

Contributors:

Julie Kalansky, CNAP/SIO/UCSD

Shrad Shukla, CNAP/UCSB

Tim Brown, WRCC/DRI

Dennis Lettenmaier, CNAP/UCLA

Amanda Sheffield, NOAA/NIDIS

 Fig. 3. A = chances of above-normal; EC= equal chances of above, 

below, normal; B = chances of below-normal. Source: cpc.ncep.noaa.gov/

For more information about NIDIS, visit the U.S. Drought Portal at www.drought.gov

Precipitation Outlook Temperature Outlook

FEB-MAR-APR MAR-APR-MAY

About this Outlook

On January 22, 2018 NIDIS and partners held the California-Nevada Drought Early Warning System Drought & 

Climate Outlook Webinar. This series provides stakeholders with updates on current and developing drought 

conditions, climatic events like El Niño and La Niña, as well as the environmental and social impacts of these 

conditions. A recording this webinar can be found at: https://www.drought.gov/drought/calendar

FEB-MAR-APR MAR-APR-MAY