# Southwest US heat wave, wildfire, and monsoon impacts > Live situation record from CLSTR: https://clstr.news/situations/arizona-heat-wave-and-response > Updated: 2026-09-09T19:21:27.000Z. Sources: 93. Developments: 27. By September 9, extreme heat and high humidity continued to impact the Southwest and Southern California. In Southern California, a high-pressure system from Arizona and offshore winds drove multiple temperature records. Long Beach reached 107 degrees, surpassing its 2015 record, while Downtown Los Angeles tied a previous record of 105 degrees. Escondido recorded its hottest day since recordkeeping began in 1893, and other areas including Camarillo, Oxnard, Santa Barbara, and Santa Maria also reported temperatures above prior marks. The National Weather Service warned of a ‘very high heat risk’ for at least one more day. The heat has impacted local infrastructure, with the Torrance Unified School District reporting record-breaking classroom temperatures. In the San Francisco Bay Area, record-breaking heat was accompanied by a smog alert due to unhealthy ozone concentrations and warnings of potential minor coastal flooding. To manage surging air conditioning demand and prevent power outages, the Los Angeles Department of Water and Power urged residents to conserve electricity. In the Desert Southwest, extreme heat warnings remained in effect for parts of Arizona, California, and Nevada, including the Las Vegas Valley, Death Valley National Park, Lake Mead, and Lake Havasu. Forecasts indicated temperatures between 106 and 112 degrees Fahrenheit, with high humidity driving ‘feels like’ temperatures between 105 and 117 degrees. Safety officials advised residents to stay hydrated and remain in air-conditioned environments, warning of lethal temperatures in car interiors. ## Claims - Peak temperatures near the coast and beaches of Los Angeles County may reach up to 100 °F. (disputed by 3 sources) - Forecasts call for valley temperatures of 100‑110 °F, interior areas 105‑112 °F, and beach temperatures in the 80‑90 °F range. (disputed by 3 sources) - Humidity levels are expected to drop to between 10% and 20%. (disputed by 3 sources) - Humidity levels remain above normal along coastal areas, contributing to the oppressive heat. (disputed by 2 sources) - The National Weather Service issued an extreme heat warning for Los Angeles County and surrounding areas from July 28 to August 2. (corroborated by 7 sources) - The National Weather Service advised the public to stay hydrated, limit outdoor activity, wear lightweight clothing, and use cooling centers. (corroborated by 5 sources) - The National Weather Service issued a red flag warning for parts of Southern California from Tuesday morning through Friday afternoon. (corroborated by 5 sources) - Heat advisory periods start at 10 a.m. Thursday July 28 and run through 8 p.m. Sunday August 2. (corroborated by 4 sources) - Forecasted temperatures include 100‑110 °F in valleys, 105‑115 °F in the Antelope Valley, and 80‑90 °F on beaches, with ocean water at 70‑74 °F. (corroborated by 3 sources) ## Timeline ### 2026-09-09: Southern California faces extreme heat and high humidity Southern California faces continued extreme heat and high humidity, with several cities setting new temperature records and public health officials issuing warnings. 2 sources. https://clstr.news/cluster/southern-california-faces-extreme-heat-and-high-humidity ### 2026-09-08: Desert Southwest faces extreme heat and high humidity Extreme heat warnings are in effect for the Desert Southwest, including parts of Arizona, California, and Nevada, with heat index values expected to reach between 105 and 117 degrees. 3 sources. https://clstr.news/cluster/desert-southwest-faces-extreme-heat-and-high-humidity ### 2026-09-08: Extreme heat and high humidity trigger warnings across California and Mississippi Extreme heat and high humidity are causing record temperatures and health warnings across California and Mississippi, prompting energy conservation requests and smog alerts in the Bay Area. 9 sources. https://clstr.news/cluster/southern-california-faces-extreme-heat-and-record-humidity ### 2026-09-08: California heat wave impacts Santa Cruz, Orange County, and Los Angeles Extreme heat waves are impacting California, with triple-digit temperatures in Santa Cruz and Orange County prompting the use of cooling centers and raising concerns over power demand and heat-related illnesses 4 sources. https://clstr.news/cluster/california-heat-wave-impacts-crops-and-coastal-regions ### 2026-09-06: Extreme Heat Warning issued for lower desert following muggy Labor Day Labor Day brings muggy conditions and light rain to the lower desert, followed by an Extreme Heat Warning from Wednesday through Friday as temperatures rise significantly above normal. 2 sources. https://clstr.news/cluster/extreme-heat-warning-issued-for-lower-desert-following-muggy-labor-day ### 2026-08-30: Desert Southwest faces severe flash flooding and monsoon storms Monsoonal moisture is causing life-threatening flash floods and debris flows across Arizona, Colorado, and Utah, resulting in fatalities, missing persons, and major infrastructure closures in the Grand Canyon. 11 sources. https://clstr.news/cluster/arizona-monsoon-triggers-flash-flood-warnings-and-rescues-in-tucson ### 2026-08-26: Southwestern US faces extreme heat and wildfire warnings Extreme heat warnings and Red Flag warnings are active across California and the Southwest, while monsoonal moisture begins to bring thunderstorms and a potential cooldown to Arizona. 10 sources. https://clstr.news/cluster/extreme-heat-warning-issued-for-desert-southwest-and-coachella-valley ### 2026-08-24: Southern California faces extreme heat wave and health warnings A major heat wave is hitting Southern California, with temperatures reaching triple digits in parts of Los Angeles and Orange Counties, prompting heat advisories and the opening of cooling centers. 13 sources. https://clstr.news/cluster/los-angeles-county-issued-heat-advisories-as-temperatures-rise ### 2026-08-23: Southwest faces extreme heat and wildfire risk A major heat wave and red flag warnings are affecting the Southwest, with extreme temperatures and high wildfire risks across Southern California, Arizona, and Nevada through the end of the week. 14 sources. https://clstr.news/cluster/southwest-california-issued-red-flag-warning-and-heat-advisory ### 2026-08-19: Desert Southwest faces extreme heat warning and storm risks An extreme heat warning is in effect for the Desert Southwest, with temperatures potentially reaching 116°F and high humidity. Monsoonal moisture may also bring storms and flooding risks. 4 sources. https://clstr.news/cluster/desert-southwest-faces-extreme-heat-warning-and-storm-risks ### 2026-08-19: Arizona faces severe dust storms and monsoon weather Severe monsoon dust storms and thunderstorms are impacting central and southern Arizona, causing power outages, hazardous visibility, and potential exposure to Valley fever-causing fungal spores. 3 sources. https://clstr.news/cluster/arizona-faces-severe-dust-storms-and-monsoon-weather ### 2026-08-15: Southwestern US faces extreme heat and wildfire risks Extreme heat and wildfire risks are spreading across Southern California and the Southwest, with temperatures expected to reach up to 114 degrees in parts of Arizona and southeast California. 9 sources. https://clstr.news/cluster/southwestern-us-faces-extreme-heat-and-wildfire-risks ### 2026-08-05: Arizona Power Rate Hike and Nationwide Heat Survey Show Rising Costs for Americans A poll shows extreme heat is hitting U.S. daily life and electricity bills, while Arizona regulators consider a 14% rate hike and policy rollbacks amid record 117 °F temperatures. 6 sources. https://clstr.news/cluster/arizona-power-rate-hike-and-nationwide-heat-survey-show-rising-costs-for-americans ### 2026-08-04: Los Angeles County Extends Extreme Heat Warning Through Early August Los Angeles County extends an Extreme Heat Warning and Heat Advisory through Aug 5, urging residents to stay hydrated, avoid peak heat, and protect vulnerable groups. 2 sources. https://clstr.news/cluster/los-angeles-county-extends-extreme-heat-warning-through-early-august ### 2026-08-04: Extreme Heat Warning Sweeps Arizona and Southwest US An Extreme Heat Warning covering Arizona’s La Paz and Yuma counties and California’s Palo Verde Valley runs until Aug 9, with temps up to 116°F, high humidity, and health advisories including cooling shelters. 2 sources. https://clstr.news/cluster/extreme-heat-warning-sweeps-arizona-and-southwest-us ### 2026-08-02: Arizona endures record heat wave, utilities report peak power demand Arizona faces a two‑week extreme‑heat warning with record temperatures, new peak power demand for APS and SRP, and health advisories as highs reach 115‑121 °F. 6 sources. https://clstr.news/cluster/arizona-endures-record-heat-wave-utilities-report-peak-power-demand ### 2026-07-30: Imperial and Yuma Valleys Under Extreme Heat Warning An Extreme Heat Warning covers Arizona's Yuma and California's Imperial valleys until Aug 3, with temps up to 120 °F, high humidity and heightened risk of heat illness for farm workers. 8 sources. https://clstr.news/cluster/imperial-and-yuma-valleys-under-extreme-heat-warning ### 2026-07-28: Extreme Heat Wave Spreads Across US, Relief Arrives in Alabama A cold front ends Alabama's heat advisory with cooler temps and showers, while Arizona faces an extended extreme‑heat warning with 110‑121 °F highs through Sunday. 3 sources. https://clstr.news/cluster/extreme-heat-wave-spreads-across-us-relief-arrives-in-alabama ### 2026-07-27: Los Angeles heat wave prompts extreme warnings and rescues An extreme heat warning covers Los Angeles County through Aug 2, with temps up to 115 °F, rising heat‑illness cases, 2,000 lifeguard rescues, and a DuraShield‑SR pavement test cutting surface heat by 16 °F. 12 sources. https://clstr.news/cluster/us-southwest-heat-wave-prompts-alerts-in-california-and-arizona ### 2026-07-21: Missouri and Arizona Issue Extreme Heat Alerts Amid 120°F Conditions Heat advisories across Missouri and an extreme heat warning for Arizona and California warn of 106‑120°F conditions, urging precautions and use of cooling shelters. 5 sources. https://clstr.news/cluster/missouri-and-arizona-issue-extreme-heat-alerts-amid-120f-conditions ### 2026-07-17: Arizona Desert Southwest Heat and Storm Threat Continues High temps and lingering humidity keep Arizona’s desert Southwest under a First Alert Weather Alert, with isolated thunderstorms possible through the week and flood risks eastward. 3 sources. https://clstr.news/cluster/arizona-desert-southwest-heat-and-storm-threat-continues ### 2026-07-09: Arizona Issues Extreme Heat Warning as Temperatures Near 115°F An Extreme Heat Warning covers Phoenix and nearby regions with temps up to 115 °F, urging precautions against heat‑related illness as monsoon moisture approaches later in the week. 3 sources. https://clstr.news/cluster/arizona-issues-extreme-heat-warning-as-temperatures-near-115f ### 2026-07-06: Arizona heat warning spurs relief centers as temperatures soar above 110°F Arizona's NWS issued an excessive heat warning for nine counties as temps hit 110‑117 °F; Salvation Army opened ten relief stations and the county runs over 250 cooling centers amid 18 heat deaths this year. 3 sources. https://clstr.news/cluster/arizona-heat-warning-spurs-relief-centers-as-temperatures-soar-above-110f ### 2026-06-30: US Cities Deploy Cooling Centers as Summer Temperatures Surge Phoenix expands to 60+ cooling centers, visited by Sen. Gallego, while Virginia opens multiple shelters and offers senior aid as heat spikes. 3 sources. https://clstr.news/cluster/us-cities-deploy-cooling-centers-as-summer-temperatures-surge ### 2026-06-23: Southwest US Endures Triple‑Digit Heat as Temperatures Surge Above 110°F Phoenix and the Southwest face triple‑digit heat with warnings up to 115°F, fire danger in Colorado, and health alerts, while gardeners are urged to water deeply, mulch, and avoid fertilizing. 6 sources. https://clstr.news/cluster/heatwave-plant-watering-guidance-for-home-gardeners ### 2026-06-11: Arizona heat wave spikes demand for RV HVAC service and triggers city emergency measures A June 2026 Arizona heat wave hit 108°F in Phoenix, prompting city cooling centers, rolling blackouts and a surge in RV HVAC maintenance at Mesa’s Cassones RV. 2 sources. https://clstr.news/cluster/arizona-heat-wave-spikes-demand-for-rv-hvac-service-and-triggers-city-emergency-measures ### 2026-06-04: Phoenix Endures Record-Breaking Spring Heat and Summer Temperatures Phoenix set a spring heat record with an 80.2 °F average, hit 112 °F in summer, saw a 15 % rise in heat‑related hospitalizations, and expanded cooling centers and community aid. 2 sources. https://clstr.news/cluster/phoenix-faces-record-breaking-spring-heat-and-summer-temperatures --- Cite as: Southwest US heat wave, wildfire, and monsoon impacts. CLSTR, https://clstr.news/situations/arizona-heat-wave-and-response