A strong upper level ridge strengthened over the Desert Southwest during the middle part of June with the center of high pressure becoming focused over the Four Corners region. As a result, temperatures warmed up well above normal reaching excessive heat conditions.
Every event with a place to put it; 34 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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.
The episode as NWS PSR wrote it up.
A strong upper level ridge strengthened over the Desert Southwest during the middle part of June with the center of high pressure becoming focused over the Four Corners region. As a result, temperatures warmed up well above normal reaching excessive heat conditions. High temperatures climbed at or above 115 degrees each day (6 days) between the 15th-20th, breaking Phoenix's record for consecutive days of 115+ degree temperatures. Temperatures in Phoenix peaked on the 17th at 118 degrees, breaking the record for the date and becoming the hottest temperature for the whole year. According to the Maricopa County Department of Public Health, sixty heat-associated fatalities occurred as a result of this heat wave.
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 Phoenix, AZ wrote its last area forecast discussion before the first event at Jun 12, 4:20 AM MST, 5 hours 40 minutes earlier.
Area Forecast Discussion
National Weather Service Phoenix AZ
420 AM MST Sat Jun 12 2021
.UPDATE...Updated Aviation Discussion.
&&
.SYNOPSIS...
A significant warm-up is expected this weekend, with extreme
temperatures lasting through next week. High temperatures across
the lower deserts are forecast to be near 110 degrees today and
then likely into a 114 to 118 degree range for most if not all of
next week. Excessive Heat Warnings are currently in effect across
south-central and southwest Arizona, as well as southeast
California through next week. Very dry conditions will persist
through at least the weekend, before chances for isolated storms
arise across the Arizona high terrain by the middle part of next
week.
&&
.DISCUSSION...
There has been little to no change in the mid-level flow pattern
over the past 24 hrs. Strong 500mb high pressure remains
positioned to the southeast of the local area. Where there was
little change the last 24 hrs, the next 24-48 hrs will feature a
great deal of change. Rapid height rises over the northern CONUS
and southern Canada will allow the strong high to amplify, drift
north, and strengthen further.
As has been advertised, the pattern progression over the next
couple of days will result in a significant increase in
temperatures, capable of tying or breaking several daily records
and not just in south-central AZ and southeast CA, but also across
the entire Southwest US. Model agreement remains very consistent
in that the central anticyclone will drift north and position in
the Four Corners region by the end of the day Monday with peak 500
mb heights around 598-600 dm by the middle of next week. Based on
ensemble mean forecasts, heights over the local CWA will peak
closer to 595-597 dm, which is still above the 99th percentile of
climatology and near record magnitudes. The thermodynamic profile
will also be near record levels as early as Sunday, especially in
the sfc-700 mb layer.
Temperatures this afternoon are expected to be 5-7 degrees warmer
than yesterday, with lower desert highs near 110F. A 110F or
greater in Phoenix today would be the first of this year and only
one day later than the normal first 110F or greater day. Another
5-7 degree increase in high temperatures is expected through early
next week, as lower desert highs are expected to reach the mid-
110s. Extreme temperatures are expected through the entirety of next
week. The inner quartile range of high temperatures from the NBM
has been consistently around 112-118F in south-central AZ through
the week and 114-122F in southwest AZ and southeast CA during the
second half of the week. There remains a 5-10% probability of
highs reaching 119-121F in the Phoenix area Mon-Fri and 120-124F
in the communities of Yuma and Imperial Valley Tue-Sat. Even if
models overperform and temperatures end up on the lower end of the
spectrum, they will still pose a significant risk and the threat
for heat-related illness is high. So, the heat this week should
be taken seriously and precaution should be taken by the entire
local population. Heat is the number one weather related killer.
Limit time outdoors as much as possible, take protective measures
for yourself, pets, and others, and hydrate frequently.
One thing that could very well keep temperatures from reaching
the upper spectrum of the model spreads is an expected increase
in moisture out of the southeast and south beginning Monday. As
the ridge center shifts to our northeast, this will likely shift
the mid level flow out of the east and southeast. The GEFS and EPS
show a gradual increase in PWATs over the area next week, with
upwards of 0.9-1.1" by Tuesday. Models also show surface dew
points in south-central AZ climbing from 10-15F this afternoon to
the upper-30s to low-40s by Tuesday. NBM continues to support
token PoPs (10-30%) mainly across the higher terrain along the
Rim, White Mtns, and portions of southeast AZ, including south of
the Phoenix area. The NBM and GEFS also support a couple hundred
J/kg of CAPE across the area by early next week. Conceivably
there may be a progression day-to-day next week as moisture
continues to increase, going from cumulus development, to weak
convection, and eventually to isolated thunderstorms by the middle
of the week. Again, with development focused primarily over
terrain features. The main impacts from any storms that do form
will be locally strong gusty winds/blowing dust and lightning,
with most rainfall not making it to the ground. Confidence is
still too low regarding exactly how much CAPE there will be, as
well as the magnitude of CIN which could keep the lower elevations
capped. So, it is still too early to say with confidence what the
rain and storm chances are in areas like Phoenix. NBM is showing
the highest 6-hrly PoPs of 10-15% during the 5PM-11PM hours,
which could easily just mean remnant showers or debris clouds with
virga after sunset.
Although there very well may be an increase in cloudiness as well
with the increase in moisture (which could hold down high temps a
bit if occurring in the afternoon), any daytime limitations will
be made up for by warmer nighttime lows (reaching around 90F in
the hottest locations by mid to late week), still resulting in
Very HeatRisk levels. An Excessive Heat Warning remains in effect
for the same times, running through next Friday.
&&
.AVIATION...Updated at 1125Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
There are no major aviation weather concerns for this TAF period
under mostly clear skies. Winds will generally follow typical
diurnal trends, with easterly winds predominating until the
westerly switch early in the afternoon. Speeds will mostly remain
AOB 9 kts with isolated afternoon gusts of 14-18 kts. At KPHX, a
few hours of a light southerly to variable wind is possible
between 17-20Z.
Southeast California/Southwest Arizona including KIPL and KBLH:
There are no major aviation weather concerns for this TAF period
under mostly clear skies. At KIPL, very light NNW to variable
winds will predominate through the morning with a few hours of an
easterly wind anticipated by the early afternoon. Westerly winds
should take hold after 00Z with a few gusts of 15-20Z through
sunset. At KBLH, extended periods of relatively light winds, AOB 7
kts, with variable directions are likely through the morning and
early afternoon. Southerly to southwesterly winds are anticipated
to predominate by 20-21Z through the rest of the TAF period.
&&
.FIRE WEATHER...
Monday through Friday:
Conditions will remain very dry with no significant chance for
wetting rains through the period. Temperatures will be near or
breaking records, with highs in the 112-118F range across the
lower deserts each day. Conditions will be driest early in the
period with Min RH around 5-10% Monday afternoon and a recovery
only to 20-25%. There will be gradual increase in moisture through
early next week, but the improvement in humidity levels will be
negligible due to the increased temperatures. Afternoon Min RH
increases a few percent and overnight Max RH remains around the
same. Winds will generally follow diurnal patterns with typical
afternoon breeziness (gusts 15-25 mph). The main forecast concern
is with the increased moisture next week, isolated dry
thunderstorms may start developing over the high terrain of
northern and eastern AZ, as well as portions of southeast AZ,
primarily after Monday. The main concerns with any storms will be
locally strong gusty and erratic winds and lightning that could
lead to new fire starts.
&&
.CLIMATE...
Daily Record Highs
Date Phoenix Yuma El Centro
------------ ------- ---- ---------
Sunday 6/13 114 (1936) 115 (1940) 118 (1940)
Monday 6/14 115 (1987) 119 (1961) 117 (1940)
Tuesday 6/15 115 (1974) 118 (1917) 115 (1940)
Wednesday 6/16 115 (1974) 119 (1917) 114 (1974)
Thursday 6/17 114 (2015) 115 (1981) 115 (1971)
Friday 6/18 115 (2015) 116 (2015) 117 (2015)
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 10 AM this morning to 8 PM MST
Friday for AZZ537-540>556-560>562.
Excessive Heat Warning from 10 AM Sunday to 8 PM MST Friday for
AZZ534-538-539-557>559-563.
Excessive Heat Warning from 10 AM Monday to 8 PM MST Friday for
AZZ530>533-535-536.
CA...Excessive Heat Warning from 10 AM Monday to 8 PM PDT Friday for
CAZ560>570.
&&
DISCUSSION...Smith/Benedict
AVIATION...AD
FIRE WEATHER...Smith/Benedict
CLIMATE...KuhlmanThe national radar mosaic for the moment the first event began.
34 excessive heat. Local standard time, as filed.
Thirty-five fatalities (27 direct and 8 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Four fatalities (3 direct and 1 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Four fatalities (3 direct and 1 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Five fatalities (3 direct and 2 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
One indirect fatality was reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Nine fatalities (6 direct and 3 indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
Two direct fatalities were reported by the Maricopa County Department of Public Health, with their details, such as age, gender, circumstances, and exact location unavailable.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, June 2021
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: 1060984, 1060985, 1060986, 1060987, 1060988, 1060989, 1060990, 1061041, 1061042, 1061043, 1061044, 1061045, 1061046, 1061047, 1061048, 1061049, 1061050, 1061051, 1061052, 1061053, 1061054, 1061055, 1061056, 1061057, 1061058, 1061059, 1061060, 1061061, 1061062, 1061063, 1061064, 1061065, 1061066, 1061067.