Name: Drought in Arizona, May 1 to 31, 2018
Start: 2018-05-01T00:00
End: 2018-05-31T23:59
Location: Arizona

Where it happened

Every event with a place to put it; 8 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 8

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 TWC wrote it up.

Extreme drought (D3 category), which began in January, continued across the same sections of southeast Arizona throughout May and expanded farther westward as light rain amounts only occurred on one day during May.

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 Tucson, AZ wrote its last area forecast discussion before the first event at Apr 30, 9:23 PM MST, 2 hours 37 minutes earlier.

Area forecast discussion, Apr 30, 9:23 PM MST, 2 hours 37 minutes before

Area Forecast Discussion
National Weather Service Tucson AZ
923 PM MST Mon Apr 30 2018

.SYNOPSIS...Breezy to windy conditions will continue the next
couple of days with cooling temperatures. There will be a chance
for showers and thunderstorms to go along with cool temperatures
Tuesday evening through Wednesday as a storm system moves across
the area. Snow levels could briefly drop below 7000 ft Wednesday.
Friday into the weekend will be dry with a rapid heating trend.

&&

.DISCUSSION...Winds continued to slowly increase today ahead of a
strong weather system digging into the region from the northwest.
The gradient tightens even more tomorrow with a wind advisory over
southern areas and a Red Flag warning for a significant portion of
the area. A shallow but strong increase in surface moisture as the
southwesterly flow gets stronger will bring higher surface dew
points tomorrow, mainly west of Tucson. This will tend to put a
damper on afternoon temperatures out west, so we lowered forecast
highs for our lower desert locations west and northwest of Tucson.
Otherwise, no updates. Please see sections below for additional
details.

&&

.AVIATION...Valid through 02/06Z.
BKN-OVC clouds above 20ft. SFC winds SWLY 12-20 kts gusting to 30
kts, gradually decreasing this evening to SLY 8-12 kts. Winds
strengthen further on Tuesday SWLY 22-28 kts with higher gusts
during the late morning into the early evening. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...The trend of breezy to windy days continues, with
the greatest wind speeds and areal extent likely occurring
Tuesday afternoon. 20-foot winds reach 20-30 mph and some
localized areas of Cochise and Santa Cruz Counties could
experience even stronger winds, especially over exposed and
elevated terrain. Showers with a slight chance of thunderstorm
development pushes through Tuesday night into Wednesday. The
highest probabilities occur north of Tucson keying in on the
higher elevations.

Breezy to windy conditions conditions continue southeast of Tucson
in Cochise County on Wednesday, finally settling down late in the
week, with gusty upslope winds at times in the afternoon due to
strong surface heating. Dry and hotter Friday into the weekend.

&&

.PREV DISCUSSION...Gusty westerly winds area wide today along
with cooler temperatures with an upper level trof axis over the
state. High level cloud cover has been on the increase this
afternoon associated with a weak vort max which was over central
California this afternoon. So expect mostly cloudy conditions this
evening then becoming partly cloudy overnight before increasing
yet again on Tuesday.

Further upstream off the Oregon coast is an upper level low which
will dive SE along the west coast over the next 24 hours with a
new upper level low developing between Vegas and LA. This feature
will gradually move east across Arizona through Thursday morning.
Surface cold front to push across the area Tuesday night, bringing
isolated to scattered showers/high elevation snow showers and a
few thunderstorms to the area. Rainfall amounts, for those areas
that see rain, will be less than two-tenths with localized higher
amounts in the higher terrain. Snow levels lowering to around 7500
feet with 1-4 inches possible above 8000 feet. Convective nature
of showers and possible thunderstorms makes it difficult to
determine which mountain range from Tucson northeast into the
White mountains will see the greater snow amounts. At this time
going with the Whites. Blowing dust a concern tomorrow also
especially across Cochise county and NW of Tucson in advance of
approaching cold front. Cooling trend to continue into Wednesday
with highs 8-12 degrees below normal for early May. Cool overnight
lows in wake of system Wednesday night into Thursday morning with
localized near freezing temperatures for an hour or two in the
usual colder valleys east of Tucson.

After this system leaves the area, its time to warm up again with
the warmest temperatures of 2018 for so on tap for this weekend
with Tucson flirting with triple digits for the first time this
year on Sunday.

Models hinting at some moisture moving up from the south across
the AZ/NM state border area Sunday into Monday. Confidence low at
this time with the scenario.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM to 7 PM MST Tuesday for AZZ151-152.

Fire Weather Watch Wednesday afternoon for AZZ151-152.

Wind Advisory from noon to 7 PM MST Tuesday for AZZ503-507-508.

&&

Meyer/JG

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The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

8 drought. Local standard time, as filed.

Drought, Tohono O Odham Nation

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Tohono O Odham Nation forecast zone
Reported by: Drought Monitor
Coordinates: 32.501, -111.567 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, Upper Santa Cruz River and Altar Valleys

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Upper Santa Cruz River and Altar Valleys forecast zone
Reported by: Drought Monitor
Coordinates: 31.812, -111.318 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, Tucson Metro Area

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Tucson Metro Area forecast zone
Reported by: Drought Monitor
Coordinates: 32.097, -111.790 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, Upper San Pedro River Valley

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Upper San Pedro River Valley forecast zone
Reported by: Drought Monitor
Coordinates: 32.109, -110.569 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, Upper Gila River and Aravaipa Valleys

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Upper Gila River and Aravaipa Valleys forecast zone
Reported by: Drought Monitor
Coordinates: 33.074, -109.563 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, White Mountains of Graham and Greenlee Counties

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: White Mountains of Graham and Greenlee Counties forecast zone
Reported by: Drought Monitor
Coordinates: 33.074, -109.563 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, Dragoon/Mule/Huachuca and Santa Rita Mountains

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Dragoon/Mule/Huachuca and Santa Rita Mountains forecast zone
Reported by: Drought Monitor
Coordinates: 31.834, -110.796 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

Drought, Baboquivari Mountains

When: May 1, 12:00 AM MST to May 31, 11:59 PM MST
Where: Baboquivari Mountains forecast zone
Reported by: Drought Monitor
Coordinates: 32.097, -111.790 (the zone’s center; the record gives no point)

Extreme drought (D3 category), which began in January, expanded during May into western Pima County and southeast Pinal County and continued across southeast Pima County, Santa Cruz County, and far southwest Cochise County including portions of the Tohono O'odham Nation and the Baboquivari, Santa Rita and Huachuca Mountains along with the White Mountains in northern Graham and Greenlee Counties and the San Carlos Apache Tribe lands of northwestern Graham County. Light rain occurred on one day in the extreme drought area during May, with rainfall amounts between a tenth and a half an inch. However, overall soil moisture readings generally decreased, with most areas ranked below the 15th percentile, with some areas below the 5th percentile. Wildfire activity continued in May with several human caused wildfires occurring in or near the extreme drought area. Levels in the San Carlos Reservoir continued to fall during May, and dropped to less than 2 percent of capacity by the end of the month.

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 Arizona in 2018 Every state in 2018 This day in weather history Warnings in Arizona, May 2018

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: 753432, 758084, 758085, 758086, 758087, 758088, 758090, 758091.