California, 2021

Drought in California, May 1 to 31, 2021

May 1 to 31, 2021 · NWS STO · 12 events in 12 counties and zones

Northern California typically experiences a wet season, October through May, and a dry season May through September. Last year's water year, October 2019 through September 2020, was one of the driest on records.

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
12

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS STO wrote it up.

Northern California typically experiences a wet season, October through May, and a dry season May through September. Last year's water year, October 2019 through September 2020, was one of the driest on records. This likely contributed to the U.S. Drought Monitor's decision to place portions of interior northern California into extreme drought on September 29, 2020. Portions of Shasta, Tehama, Butte, Glenn, Colusa, Yolo, Solano, Yuba, Nevada, and Sacramento counties remain in extreme drought. The rest of interior northern California was placed into severe drought (D2) on December 8; however, the state of California has not announced that these locations are in drought. On 4/21/2021 the Biden-Harris administration announced the formation of an Interagency Working Group to address worsening drought conditions in the West. On 5/10/2021 Governor Gavin Newsom significantly expanded his April 21 drought emergency proclamation to include Klamath River, Sacramento-San Joaquin Delta and Tulare Lake Watershed counties where accelerated action is needed to protect public health, safety and the environment. In total, 41 counties are now under a drought state of emergency, representing 30 percent of the state’s population.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Sacramento, CA wrote its last area forecast discussion before the first event at Apr 30, 9:59 PM PST, 2 hours 1 minute earlier.

Area forecast discussion, Apr 30, 9:59 PM PST, 2 hours 1 minute before
Area Forecast Discussion
National Weather Service Sacramento CA
1059 PM PDT Fri Apr 30 2021

.SYNOPSIS...
Dry and above normal weather are forecast to prevail through the
rest of the week. Gusty offshore winds possible Sunday and Monday
could bring critical fire weather concerns, particularly for the
Sacramento Valley

&&

.DISCUSSION...
The Evening Update: Satellite indicates a couple of short waves will
be moving through Norcal in the near term. Initial system nearing
the coast is associated with a little rain band which for the most
part will erode as it moves inland. This system could provide enough
momentum to push the marine layer into the Srn Sac Vly. Ft Ord
indicates the M.L. depth is above 2 kft and if the KSUU winds
continue to howl overnite (as the Lamp guidance indicates) in the
least a patchy stratus intrusion into the Srn Sac Vly is possible.

Second short wave moving over Norcal Sat afternoon may trigger an
isolated shower or two or a brief TRW in portions of zone 13, and
possibly a better chance in zone 14, per the GFS CAPE/LI progs. Have
updated evening grids to account for these possibilities.   JHM

.Previous Discussion...
GOES-West visible satellite imagery reveals a band of high clouds
passing over northern California this afternoon. These clouds are
arriving in advance of an approaching upper level trough that will
arrive this weekend -- more on that later...

In the short-term, another day with well-above normal temperatures
can be expected for northern California. The upper level ridge
responsible for producing these temperatures has flattened over
the last day, and axis is more centered over southern California.
For our area, temperatures will generally be within a few degrees
of what was observed yesterday with upper 80s to low 90s in the
Sacramento and northern San Joaquin Valley, or about 15 deg F
above late April normals.

On Saturday, an shortwave trough will approach the northern
California coast. Most locations should see a few/several degrees
of cooling from today to Saturday, though, highs will still be a
solid 8 to 12 deg F above normal. Additionally, can't rule out a
slight chance of shower in far northern Shasta County, the
southern Cascades, and far northern Sierra. Most populated areas
will remain dry. Increased onshore flow will benefit the Delta
region and portions of the Sacramento Valley on Saturday.
Unfortunately, this onshore flow will be short-lived...

In the wake of the shortwave's passage, northerly surface
pressure gradients will strengthen, and will consequently raise
fire weather concerns. Forecast models advertise the onset of
increasing northerly winds in Sacramento Valley after midnight
Sunday and into the day on Sunday. This dry winds will cause
relative humidity values to plummet, especially during the
afternoon hours. Another thing to note: the dry vegetation/fuels.
While we did get a temporary break from the extremely high energy
release components (ERCs) from last weekend's system, the dry
northerly winds will allow the ERCs to race back up toward
climatological records for this time of year. ERCs are an
excellent fuel status indicator -- the higher the ERCs, the more
available energy.

All this considered, a Fire Weather Watch has been issued for the
Sacramento Valley as well as portions of the northern San Joaquin
Valley, and up to about 1,500 ft elevation. Watch begins 11 AM
Sunday and goes through 5 PM PDT Tuesday as periods of gusty
northerly winds are forecast to linger into early next week.
Expect afternoon relative humidity values to fall to near 10
percent, locally lower each afternoon from Sunday through Tuesday.
While the calendar says it is only late April / early May, the
winds, RHs, and fuels are all there -- critical fire weather
conditions have the potential to return this weekend. // Rowe

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...
Ensemble guidance favors the return of a ridge in the eastern
Pacific for the middle of next week, which would boost
temperatures back up into the upper 80s to low 90s in the Valley.
Can't rule out some locations making a run for the middle 90s on
next week Wednesday. Clusters generally shift the ridge inland
toward the Intermountain West on Thursday. Forecast confidence
drops off on Friday as clusters advertise different solutions.

&&

.AVIATION...
VFR conditions for the next 24 hrs. Surface winds generally below
15 kts, except for in the vicinity of the Delta where gusts up to
20 to 30 knots are possible after 00Z.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Sunday morning through Tuesday afternoon
for Carquinez Strait and Delta-Central Sacramento Valley in
Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below
1000 Ft-Northern Motherlode From 1000 to 3000 Ft. Includes
portions of Nevada-Yuba-Placer-Amador and ElDorado Units-
Northern Sacramento Valley to Southern Tehama County Line Below
1000 Ft-Northern San Joaquin Valley in San Joaquin and
Stanislaus Counties Below 1000 ft-Northern Sierra Foothills from
1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte
Units-Southern Sacramento Valley in Yolo-Sacramento Far Western
Placer, southern Sutter and Solano County Below 1000 Ft.

&&

Event by event

12 drought. Local standard time, as filed.

Drought, Northern San Joaquin Valley

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Northern San Joaquin Valley forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor put part of San Joaquin County, zone 19, in exceptional drought (D4). The rest of the zone was placed into extreme drought (D3).They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. On May 10th, governor Gavin Newsom included all of zone 19 in the official drought emergency proclamation.

Drought, Mountains Southwestern Shasta County to Western Colusa County

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Mountains Southwestern Shasta County to Western Colusa County forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed roughly half of zone 63, which covers western Tehama, Glenn, and Colusa counties in exceptional drought (D4) while the rest of the zone remains in extreme drought (D3). They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. On May 10th, governor Gavin Newsom included all of zone 63 in the official drought emergency proclamation.

Drought, Carquinez Strait and Delta

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Carquinez Strait and Delta forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor put all of zone 18 in exceptional drought (D4). They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. A giant rock wall will be constructed across a river in the Sacramento-San Joaquin River Delta to protect a vital freshwater estuary from saltwater as rivers become too low to push the brackish waters from the bay. The $30 million barrier will be built in the same place as it was in 2015 on the West False River to keep saltwater away from pumping stations. This will protect a water source for nearly 30 million Californians. Construction slated to begin by June 1 and be complete by July 1. The barrier will be removed before Nov. 30. Farmers north and south of the Sacramento-San Joaquin River Delta will receive no water from the Central Valley Project. The agency previously had forecast a 5% allocation. On May 10th, governor Gavin Newsom included all of zone 18 in the official drought emergency proclamation. The Delta cross channel gates were closed on May 20th.

Drought, Southern Sacramento Valley

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Southern Sacramento Valley forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor put all of zone 17, which includes portions Yolo, Solano, Sutter, and Sacramento County in exceptional drought (D4). They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. Sacramento residents have been asked to reduce their water usage by 10%. The area saw: reduced forage, decreased water allocation, decreased stock weights, selling of livestock, early shipping of cattle to summer range, hauling of water, low rivers/ponds/springs, and installation of new wells. On May 10th, governor Gavin Newsom included all of zone 17 in the official drought emergency proclamation.

Drought, Central Sacramento Valley

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Central Sacramento Valley forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor put all of zone 16 in exceptional drought (D4). They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. Some of the impacts to the region included: removal of houseboats from Lake Oroville, reduced forage, decreased water allocation, decreased stock weights, selling of livestock, early shipping of cattle to summer range, hauling water, and low to dry rivers/ponds/springs. On May 10th, governor Gavin Newsom included all of zone 16 in the official drought emergency proclamation.

Drought, Northern Sacramento Valley

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Northern Sacramento Valley forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor put all of zone 15, portions of Shasta and Tehama counties, into exceptional drought (D4).They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. The Bella Vista Water District reported penalties unless water usage reduced by 10%. Some of the other impacts the region saw included: reduced forage, decreased stock weights, selling of livestock, livestock stress, reduced grazing on public lands, reduced market price for cattle, and increased pricing for small grain and hay crops. The area also saw: decreased water allocation, hauling of water, increased groundwater use, land subsidence, low to dry rivers/ponds/springs, dry wells, and installation of new wells. On May 10th, governor Gavin Newsom included all of zone 15 in the official drought emergency proclamation.

Drought, Burney Basin/Eastern Shasta County

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Burney Basin/Eastern Shasta County forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed zone 14, which covers northeast Shasta County, in both extreme and exceptional drought (D3 and D4).They mentioned that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. On May 10th, governor Gavin Newsom included all of zone 14 in the official drought emergency proclamation.

Drought, Shasta Lake/North Shasta County

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Shasta Lake/North Shasta County forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed the majority of zone 13, which covers Shasta County, in exceptional drought (D4). They continue to mention that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. Shasta Lake storage levels remain low and the city of Shasta Lake had its water allocation cut by 45% forcing acquisition of alternative water sources. On May 10th, governor Gavin Newsom included all of zone 13 in the official drought emergency proclamation.

Drought, Northeast Foothills/Sacramento Valley

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Northeast Foothills/Sacramento Valley forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed zone 66, which covers the northeast foothills and portions of the Sacramento Valley, in both extreme and exceptional drought (D3 and D4).They mentioned that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. On May 10th, governor Gavin Newsom included all of zone 66 in the official drought emergency proclamation.

Drought, Motherlode/Camptonville to Groveland

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Motherlode/Camptonville to Groveland forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed zone 67, which covers the Motherlode, in extreme drought (D3 ).They mentioned that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. The area saw: reduced forage, decreased water allocation, decreased stock weights, and hauling of water. On May 10th, governor Gavin Newsom included all of zone 67 in the official drought emergency proclamation.

Drought, Mt Shasta/Western Plumas County

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
Mt Shasta/Western Plumas County forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed zone 68, which covers the western Plumas County and Lassen National Park, in extreme drought (D3 ).They mentioned that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. On May 10th, governor Gavin Newsom included all of zone 68 in the official drought emergency proclamation.

Drought, West Slope Northern Sierra Nevada

When
May 1, 12:00 AM PST to May 31, 11:59 PM PST
Where
West Slope Northern Sierra Nevada forecast zone
Reported by
Drought Monitor

For the month of May, the U.S. Drought Monitor placed zone 68, which covers the west slope of the Sierra Nevada, in extreme drought (D3 ).They mentioned that we will see drought impacts expand into the summer, including but not limited too: agriculture, water supplies, recreation, and ecosystems. They also started noting concern for the upcoming wildfire season and that drought preparedness is key since given back-to-back dry years. On May 8th, Tuolumne County proclaimed a local emergency due to drought. On May 10th, governor Gavin Newsom included all of zone 69 in the official drought emergency proclamation.

What these are

Drought
A drought reaching severe (D2) or worse on the US Drought Monitor, or with notable impacts.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, May 2021

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 960711, 960712, 962283, 962284, 962285, 962371, 962372, 962373, 962374, 962377, 962385, 962386.