High pressure over the Southwest allowed for temperatures across the Phoenix area to warm up above 100 , which is about 7-10 degrees above normal for this time of the year. On the 13th, Phoenix officially hit 102 , making it the warmest temperature recorded up to this point in the year and the warmest temperature during the month.
Every event with a place to put it; 4 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.
High pressure over the Southwest allowed for temperatures across the Phoenix area to warm up above 100 , which is about 7-10 degrees above normal for this time of the year. On the 13th, Phoenix officially hit 102 , making it the warmest temperature recorded up to this point in the year and the warmest temperature during the month. According to the Maricopa County Department of Public Health, five heat-associated fatalities occurred during this event.
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 May 12, 4:56 PM MST, 4 minutes earlier.
Area Forecast Discussion National Weather Service Phoenix AZ 456 PM MST Wed May 12 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... High pressure will build across the region over the next couple days leading to a modest warming trend and high temperatures mostly ranging between 100 to 103 degrees through Friday. A bit of moisture moving into eastern Arizona will bring a slight chance for showers and thunderstorm to the higher terrain east of Phoenix on Friday afternoon. However, any storms that do form are expected to produce little, if any rainfall. The approach and passage of an upper trough over the coming weekend into early next week will lead to a cooling trend along with more breezy to locally windy conditions. Dry conditions will mostly prevail through the period, but chances for a few showers and thunderstorms may return to the Arizona high terrain by Sunday or Monday. && .DISCUSSION... An upper level ridge just off the West Coast will continue to spread over the region from this afternoon into Thursday with 500mb heights eventually topping out around 585dm on Thursday. This incoming ridge is nothing atypical for this time of year with the max heights barely making it into the 90th climatological percentile. The warmer air mass under the ridge will push daytime highs back to around 100 degrees for the lower deserts this afternoon and then mostly into a 100-103 degree range for Thursday and Friday. Although very dry conditions will persist over the next few days for most areas, models are continuing to show a slight moisture uptick into far eastern Arizona for Friday. Some of this moisture likely will be from the remains of tropical storm Andres, which dissipated well off the coast of Mexico yesterday. Andres is the earliest recorded eastern Pacific tropical storm in the eastern Pacific (reliable records date back to the early 1970's). This increase with low level mixing ratios only up to around 5 g/kg should also coincide with a very weak and broad shortwave trough undercutting the ridge on Friday, potentially moving across southern Arizona and northern Mexico. If this solution holds true, there may be a few high based showers and thunderstorms across far eastern Arizona and potentially across eastern Gila County Friday afternoon. Any storms that do form are expected to produce very little rainfall, with the greater threat being elevated fire danger levels due to dry lightning. While the ridge is getting undercut and also partially ejecting eastward into the Southern Plains, models continue to trend towards better-and-better agreement that a more organized trough will dive southeastward into northern California Friday night. Model ensembles agree this trough will continue to track southeastward over AZ the weekend, eventually becoming a closed low and likely slowing its progression. However, some differences remain with the timing of the system, but confidence of the system impacting our region continues to increase. Unsurprisingly, moisture levels will be quite low initially, likely preventing any rain chances on Saturday, and probably even Sunday. Ensembles continue to present the best chance for any shower or thunderstorm activity on Monday as the upper low center passes over AZ. For now, the likely low moisture levels should only favor convection over the Arizona high terrain. Temperatures will definitely trend lower over the weekend, likely falling back to normals or just below for Sunday and Monday. An unsettled weather pattern may persist through the middle of next week as a good portion of the ensemble output indicates a potential second trough moving into the Western U.S. around next Wednesday && .AVIATION...Updated at 2350Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: winds will remain mostly light and generally follow normal diurnal trends through the period. Periods of light and variable conditions are also expected including tomorrow from mid morning to mid afternoon before the westerly switch. A few isolated westerly gusts into the mid teens are also possible briefly early Thu evening. Skies to remain clear until a few high clouds could move through late tomorrow afternoon. Sunset/sunrise slantwise visibility degradation may occur due to area wildfires. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected through the period. Light, diurnal winds, mostly below 10 kts, will persist through the TAF period with KIPL favoring the southeast and KBLH favoring the south. Some afternoon/evening breeziness with speeds near 10-15 kts will be possible at the sites before subsiding later tonight. Clear skies will persist through at least tomorrow morning. && .FIRE WEATHER... Saturday through Wednesday: Temperatures on Saturday will be in the upper 90's, then lowering closer to 90 degrees by Sunday and MOnday as a weather system moves into the region. This weather system may provide a small chance for a few isolated thunderstorms as well, likely focused over the Arizona high terrain. Winds early in the period will be fairly breezy during the daytime hours with afternoon gusts commonly 20-25 mph and up to 30 mph possible across southeast California on Saturday. For the lower deserts, dry conditions will remain through the period with minimum RHs mostly in the single digits through Saturday before improving into the 10-15% range on Sunday and Monday. Maximum RH values will commonly be around 15-25% through Saturday, likely improving to 25-40% on Sunday and Monday. Somewhat drier and warmer conditions can be expected on Tuesday and Wednesday as high pressure attempts to build back northward across the region. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && DISCUSSION...Kuhlman/Percha AVIATION...Sawtelle/D'Anthony FIRE WEATHER...Smith/Kuhlman/Percha
The national radar mosaic for the moment the first event began.
4 heat. Local standard time, as filed.
One direct fatality was reported by the Maricopa County Department of Public Health, with their details, such as age, gender and circumstances unavailable.
Two fatalities (one direct and one indirect) were reported by the Maricopa County Department of Public Health, with their details, such as age, gender and circumstances unavailable.
One direct fatality was reported by the Maricopa County Department of Public Health, with their details, such as age, gender and circumstances unavailable.
One direct fatality was reported by the Maricopa County Department of Public Health, with their details, such as age, gender and circumstances unavailable.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Heat, Central Phoenix | 2021-05-12 | Unknown | Direct | ||
| Heat, North Phoenix/Glendale | 2021-05-13 | Unknown | Direct | ||
| Heat, North Phoenix/Glendale | 2021-05-13 | Unknown | Indirect | ||
| Heat, North Phoenix/Glendale | 2021-05-14 | Unknown | Direct | ||
| Heat, North Phoenix/Glendale | 2021-05-16 | Unknown | Direct |
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, May 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: 1057126, 1057127, 1057128, 1057129.