Southwest March Heat Wave That Hit 110°F Near Martinez Lake Tied to Human-Caused Climate Change, Studies Find
The March Southwest heat wave produced a record 110°F near Martinez Lake, Arizona—the highest March temperature ever recorded in the U.S.—and shattered or tied numerous local March highs across California, Nevada and Arizona (including North Shore at 108°F, Phoenix’s earliest triple‑digit readings, Las Vegas and Palm Springs), with many locations 20–30°F above normal and more than 41 million people under heat alerts. Researchers, including the World Weather Attribution group, say the event would have been virtually impossible without human‑caused climate change, and NOAA/AP analyses show a marked rise in heat records and the area and cost of extreme weather in recent decades.
📌 Key Facts
- On March 18–20, 2026, an intense Southwest heat wave set and broke U.S. March temperature records: North Shore, California, hit 108°F on March 18 (tying the 1954 Rio Grande City, Texas, March record), and the National Weather Service reported 110°F (43.3°C) recorded near Martinez Lake, Arizona, in the Yuma Desert — the highest March temperature ever recorded in the United States.
- Multiple desert and city records were reported across the region: Cathedral City and Thermal, CA, reached 108°F (Thermal was forecast to reach 110°F), downtown Los Angeles hit 94°F, Palm Springs reached 104°F (tying its March record), and Phoenix had its earliest triple‑digit March readings (101°F reported then 105°F, marking new March records); Las Vegas also set a new March high (reported near the upper 90s).
- The heat wave pushed temperatures roughly 20–30°F above normal for March across large parts of the Southwest, prompting the National Weather Service to call it "one of the most significant March heat waves in recorded history" with many records broken in a short span.
- More than 41 million people were under heat alerts through the following weekend, and heat impacts forced public‑safety actions such as closing Phoenix hiking trails because of elevated heat‑illness risk.
- World Weather Attribution concluded this March Southwest heat wave would have been virtually impossible without human‑caused climate change, attributing the extreme event to the influence of warming from greenhouse gases.
- Broader climate and impacts context: AP analysis of NOAA data shows the U.S. is now breaking 77% more hot‑weather records than in the 1970s and 19% more than in the 2010s; NOAA’s Climate Extremes Index finds the area of the U.S. hit by extreme weather in the past five years has doubled compared with 20 years ago; and NOAA/Climate Central data show the number and inflation‑adjusted average cost of U.S. billion‑dollar weather disasters in recent years is about twice the level of a decade ago and nearly four times that of 30 years ago.
- Climate experts, including those at Climate Central and former FEMA leadership, warn these extremes are pushing beyond historical planning assumptions and are increasingly "outside the historical playbook," complicating preparedness and response.
📊 Relevant Data
Non-Hispanic Black individuals in the US have a higher rate of heat-related mortality compared to non-Hispanic White individuals, with disparities varying by region.
Heat-related mortality rates per 100,000 population increased during 2019-2023 among Hispanic populations with an average annual percent change of 28.7%.
Trends in Rates of Heat-Related Deaths Across Population Groups, United States, 2019-2023 — SAGE Journals
Black, Latinx, and Native American individuals have an elevated risk of dying from higher temperatures and extreme heat events compared to White individuals.
Racial Disparities in Climate Change-Related Health Effects in the United States — PMC
Evidence of racial differences in heat tolerance due to genetic factors is inconclusive, with disparities more attributable to environmental and socioeconomic conditions.
Racial and socioeconomic disparities in heat-related health effects and their underlying causes — PMC
📰 Source Timeline (5)
Follow how coverage of this story developed over time
- World Weather Attribution group finds the March Southwest heat wave would have been virtually impossible without human-caused climate change.
- AP analysis of NOAA data shows the U.S. is now breaking 77% more hot weather records than in the 1970s and 19% more than in the 2010s.
- NOAA’s Climate Extremes Index shows the area of the U.S. hit by extreme weather in the past five years has doubled compared with 20 years ago.
- NOAA and Climate Central data indicate the number and inflation-adjusted average cost of U.S. billion‑dollar weather disasters in the last couple of years is twice as high as a decade ago and nearly four times higher than 30 years ago.
- Experts, including Climate Central’s Bernadette Woods Placky and former FEMA Administrator Craig Fugate, characterize current extremes as pushing beyond historical planning assumptions and "outside the historical playbook."
- National Weather Service reports 110°F (43.3°C) recorded near Martinez Lake, Arizona, in the Yuma Desert, now the highest March temperature ever recorded in the United States.
- The previous 108°F March record, set in Rio Grande City, Texas in 1954 and tied Wednesday at North Shore, California, was surpassed on Thursday.
- Additional California desert locations, including Cathedral City and Thermal, hit 108°F Thursday, with Thermal forecast to reach 110°F on Friday.
- Phoenix reached 105°F Thursday, breaking the 102°F March record set the day before and marking its earliest triple‑digit day on record; Las Vegas hit 95°F, also a March record.
- Phoenix hiking trails were closed Thursday because of heat‑illness risk as temperatures across the Southwest stayed 20–30°F above normal for March.
- Confirms the record-tying 108°F reading occurred in North Shore, California, explicitly naming the community.
- Notes that more than 41 million people remain under heat alerts through Sunday, according to CBS News meteorologist Nikki Nolan.
- Provides additional city-level records: Las Vegas hit 99°F (breaking its prior March record of 93°F), downtown Los Angeles reached 94°F (beating a 1997 daily record of 87°F), and Palm Springs hit 104°F (tying its March record from 1966).
- Reports Phoenix’s earliest-ever triple-digit reading in March at 101°F on Wednesday, breaking the previous March 26, 1988 record and marking only the second March 100°F day on record there.
- Quotes NWS meteorologist Bryan Lewis calling this "one of the most significant March heat waves in recorded history" and emphasizing how many daily records have already been broken.
- Projects that the aptly named Thermal, California, was forecast to reach 110°F on Friday and that many other cities may see their earliest 100°F day on record, with temperatures staying 20–30°F above normal into the weekend.
- North Shore, California, hit 108°F on Wednesday, March 18, 2026, tying the highest March temperature ever recorded in the United States, previously set in Rio Grande City, Texas, in 1954.
- The nearby community of Thermal, California, is forecast to reach 110°F on Friday, which would break the existing March record if realized.
- Phoenix reached 101°F on March 18, its earliest 100-degree day on record and only the second time it has hit triple digits in March (the previous was 100°F on March 26, 1988).
- Las Vegas reached 99°F, setting a new all‑time March record and breaking its prior March high of 93°F from 2022.
- Downtown Los Angeles hit 94°F, surpassing its previous daily record of 87°F set in 1997, while Palm Springs reached 104°F, tying its hottest March day on record from 1966.
- NWS meteorologist Bryan Lewis said this is one of the most significant March heat waves in recorded history, with many locations running 20–30°F above normal and “so many records” being broken in a short span.