Strong high pressure over the Desert Southwest led to temperatures climb well above normal as afternoon high temperatures topped out above 100 degrees. On the 6th, Phoenix reached 106 degrees, tying the daily record high for the date.
Every event with a place to put it; 22 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.
Strong high pressure over the Desert Southwest led to temperatures climb well above normal as afternoon high temperatures topped out above 100 degrees. On the 6th, Phoenix reached 106 degrees, tying the daily record high for the date. According to the Maricopa County Department of Public Health, one heat-associated fatality 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 3, 10:10 PM MST, 1 hour 50 minutes earlier.
Area Forecast Discussion...Updated National Weather Service Phoenix AZ 1010 PM MST Sun May 3 2020 .UPDATE...Updated aviation discussion. && .SYNOPSIS... The unseasonably warm temperatures will continue through next week. High temperatures across the lower deserts will be in the upper 90s to near 100 degrees through tomorrow and then climb into the mid 100s by the middle of next week. Mostly clear skies will prevail. The hot and very dry conditions combined with very dry vegetation will cause heightened brush fire potential for at least the next 7 days. && .DISCUSSION... Through Monday, a series of weather disturbances will move across the northwest CONUS, placing the desert southwest under warm and dry west flow. Despite this leading to slightly lower heights over our neck of the woods, 500 mb heights still remain above the 90th percentile for this time of year, resulting in high temperatures running close to 10 degrees above normal. Breezy conditions this afternoon and early evening may lead to very localized areas of blowing dust, especially in southeast California. Dry flow will keep skies clear, with a few high clouds moving through from time to time. These clear skies overnight will allow our temperatures to drop into the 60s both tonight and tomorrow night. Strong ridging will build north into our region Tuesday and Wednesday leading to hotter temperatures. 500 mb heights across our forecast area will rise above the 99th percentile and lead to near-record high temperatures. Right now, it appears that both Phoenix and Yuma may break their previous records on Wednesday, with forecast highs near 108 degrees. For reference, the warmest temperature ever recorded in Phoenix in May is 114 degrees and this was back in 1910. In Yuma, the warmest temperature ever recorded in May is 120 and this was also in 1910. With limited cloud cover, temperatures will cool 30-40 degrees overnight providing good relief. There will be very subtle weakening of the ridge Thursday due to a short wave passing far to the north. Thus, there will be very little change in temperatures Thursday. This will lead to 24 hr Heat Risk values well into the Moderate category (approaching the high category). Late this week, the ensemble models depict slight cooling in part due to heights/thicknesses being subtly lower but also due to an increase in atmospheric moisture from Mexico. There is already some moisture over northern Mexico. Models are depicting that this will be enhanced by a front that will spill down the Plains. They also show weak upper troughing within a southern branch of the Westerlies developing near Baja. This feature (and perhaps another weak upper low originating from central/southern Mexico) helps advect moisture northward into Arizona. In fact, the ECENS mean is depicting very light precip over isolated higher terrain areas outside of our forecast area as early as Friday (mainly White Mountains). On Saturday, it has a larger area of very light precip (still over the higher terrain barely touching our CWA). This is a reflection of model convection since ridging will still be in place. Of note, only some ECENS members are depicting precip which leads to a non-zero average/mean in the aforementioned areas. That being said, there are more members showing precip now than there were 24 hours ago. The GEFS is slower to bring the moisture northward as it has a mean position of the weak trough further west. This is likely due to its mean solution of the large scale pattern slightly further west (ridge axis and central/eastern CONUS trough extending a bit further west). Convection is much more likely over the Sierra Madre. But, if it materializes over Arizona, it would likely struggle to produce any decent precip and would probably be more effective at wind production. && .AVIATION...Updated at 0510Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Very dry westerly flow aloft will continue to keep skies basically clear over the next 24 hours. Maybe a few wisps of thin cirrus at times but nothing of consequence. Winds will continue to follow the same diurnal trends as seen over the past couple of days, with light west wind returning to the east or southeast after about 08z. Winds at KPHX probably won't become east until after 10z or so. Expect another return to west wind Monday afternoon after about 20z with speeds slightly less than today. Cannot rule out a gust or two late Mon afternoon into early evening with speeds into mid teens. Basically continued to use persistence for the most part when preparing the 06z TAF package. Southeast California/Southwest Arizona including KIPL and KBLH: Dry westerly flow aloft will continue to keep skies clear across the western deserts through at least the next 24 hours. There may be a few wisps of thin cirrus at times but nothing of any consequence to aviation. Winds at KIPL will be light west mostly less than 10kt rest of tonight and into Monday morning. Winds to become more northwest during late morning Monday but speeds mostly below 10kt. At KBLH, we should see southwest winds to around 10kt diminishing and turning to the west or northwest by midnight. Model signals continue to suggest a period of LLWS after 08z at KBLH with winds up to 35kt at 2k feet combined with northwest winds around 06z at the surface (due to decoupling). After 13z or so the shear should fall below criteria and thus will be removed from the TAF. Winds likely to favor the north to northwest most of the day on Monday with speeds generally 10kt or less. && .FIRE WEATHER... Wednesday through Sunday: Very warm afternoon temperatures will exist through the period, with lower elevation max temperatures in the 105-108 range Wednesday and Thursday. Wednesday through Friday, minimum humidities will be in the single digits - even over higher terrain. Max humidities will only be in the 15-25% range most places. Saturday and Sunday an increase in humidities is expected along with slightly cooler high temperatures. The humidity increase will not be dramatic (about 5-10%) but there may be just enough atmospheric moisture for thunderstorms to develop over the White Mountains, Rim, and southeast AZ Saturday and Sunday. If so, they could produce outflow winds that could reach southern Gila County and the eastern fringes of Maricopa and Pinal counties. Apart from any thunderstorm activity, winds will be relatively light except for typical warm season breezes in the afternoons and evenings. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && DISCUSSION...Feldkircher/AJ AVIATION...CB FIRE WEATHER...AJ
The national radar mosaic for the moment the first event began.
21 excessive heat, 1 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.
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 | 2020-05-04 | Unknown | Direct | ||
| Excessive Heat, Central Phoenix | 2020-05-06 | Unknown | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2020Every state in 2020This day in weather historyWarnings in Arizona, May 2020
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: 985841, 985818, 985819, 985820, 985821, 985822, 985823, 985824, 985825, 985826, 985827, 985828, 985829, 985830, 985831, 985832, 985834, 985835, 985836, 985837, 985838, 985839.