US Southwest Climate – July 2026 Update
Top States: Arizona, Colorado, New Mexico, and Utah
Summary
Record heat and expanding high-pressure systems baked the American Southwest over the recent month, pushing regional average temperatures more than two degrees Celsius above long-term baselines. Persistent trapped searing heat across the Four Corners region, accelerating soil moisture loss and stressing major water systems across the Colorado River Basin. Meanwhile, monsoonal surges brought isolated heavy downpours and localised flash flooding to desert terrain. This regional warmth arrives alongside a moderate El Niño forecast to peak at Very Strong in Sep-Nov, which may alter regional precipitation patterns as autumn approaches.
This month in numbers
The US Southwest registered a 1-month average temperature anomaly of +2.26°C above the 1961-1990 baseline, marking an exceptionally warm month for the region. Over broader timeframes, the 3-month anomaly stood at +2.12°C, while the 12-month rolling anomaly reached +3.13°C. In a global context, 7 of the top 10 warmest regions globally over the past 12 months were US states, with several Southwestern states dominating the upper ranks of global temperature departures.
Hottest & coolest US states
State-level statistics highlight broad warmth across the entire regional group. Utah US Utah recorded the highest 1-month anomaly at +2.66°C, followed closely by Colorado US Colorado at +2.45°C, where widespread areas experienced their 2nd warmest July on record. New Mexico US New Mexico registered a temperature anomaly of +2.39°C, while Arizona US Arizona recorded +1.65°C above baseline. None of the member states in the Southwestern group experienced below-average monthly temperatures.
What's driving change?
Multiple atmospheric and land drivers contributed to the sustained heat across the region. Dominant trapped hot air over the interior West, while reduced natural evaporative cooling in arid rangelands. At higher altitudes, continues to accelerate temperature gains across mountain ranges. Tropical systems also made a brief appearance; all of US Southwest's 1 tropical cyclone this year occurred in the past month, as tracked on our live map at Extreme Weather tracker. On a tropical scale, ENSO remains active in a moderate El Niño phase with a RONI anomaly of +0.98°C, which historically brings a 60% likelihood of wetter winter conditions to the Southwest USA that could help replenish depleted reservoirs.
Looking ahead
Seasonal forecasts from NOAA's Climate Prediction Center indicate an increased probability of above-normal monsoonal precipitation across parts of the Four Corners states over the next 1 to 3 months, offering potential short-term drought relief alongside lingering warmth.
Generated by Gemini from climate data and web sources
At a Glance
Temperature – Average
Climate Map – USUnited States
Source: NOAA Climate at a Glance — US states & climate regions (tavg, pcp), plus GPCC (Snow, water-equivalent). Anomalies are vs the 1961–1990 baseline. See methodology.
Long-Term Trends
Combined Timeline – US Southwest
Precipitation, Sunshine, Frost and Snow are converted to standard deviations from their own average so they can share an axis with Temperature.
NOAA Climate at a Glance - regional tavg / pcp
Heatwave Days – US Southwest
Warm Spell Duration Index (WSDI) - days in a 6+ day run above the local 90th-percentile temperature for that time of year.
Data: World Bank Climate Change Knowledge Portal (ERA5-derived), aggregated by 4BYO across member states. Refreshed roughly 1-2x/year, ~7-8 months behind present.
Hottest & Coolest in US Southwest this Month
1-month anomaly vs 1961–1990 across the 4 members we cover. Click a name to open its profile.
Warmest
- 1.🇺🇸Utah+2.66°C
- 2.🇺🇸Colorado+2.45°C
- 3.🇺🇸New Mexico+2.39°C
- 4.🇺🇸Arizona+1.65°C
Coolest
- 1.🇺🇸Arizona+1.65°C
- 2.🇺🇸New Mexico+2.39°C
- 3.🇺🇸Colorado+2.45°C
- 4.🇺🇸Utah+2.66°C
Year-on-Year Trends
The 4byo Climate Helix – US Southwest
NOAA Climate at a Glance — regional tavg / pcp (monthly absolutes).
Monthly Temperature – US Southwest
Background lines show the last 40 years (plus the record year and its opposite, wherever they fall).
NOAA Climate at a Glance — regional tavg / pcp (monthly absolutes).
Records – US Southwest
NOAA Climate at a Glance - regional tavg / pcp - Anomalies vs 1901-2000 mean
Shifting Seasons
Warm / cold seasonsHow spring and autumn have shifted in US Southwest. Spring is defined as the date monthly temperatures first rise above the long-term annual mean (10.8°C, from 1950–1979); autumn is the date they fall back below it. Temperature swings 23.3°C peak-to-peak across the year - a classic four-seasons rhythm.
Baseline vs recent monthly temperature climatology. Biggest warming: Dec (+2.0°C).
NOAA Climate at a Glance — regional tavg. Baseline: first 30 yrs on record. Recent: last 10 yrs on record.
Climate Systems
Loading ENSO tracker…
Emissions & Energy
Explore
Explore Climate Data
Data Sources
Data Sources for US Southwest
Every figure on this page is sourced from official, openly published climate datasets. Anomalies are calculated against the 1961–1990 baseline (temperature) and 1991–2020 (rainfall, sunshine, frost) - see the Methodology & Sources page for the complete dataset list and update calendar.
US 9-region temperature and precipitation series (1895–present).
US state-level CO₂ emissions and electricity generation mix by fuel source. Energy Information Administration.
Frost Days and Heatwave Days (Warm Spell Duration Index), ERA5-derived. World Bank Climate Change Knowledge Portal.
Monthly snow water-equivalent, Global Precipitation Climatology Centre (DWD).
FAQs
FAQs
How is the climate in US Southwest changing?
US Southwest is warming in line with the rest of the world. The page above shows the latest monthly temperature anomaly versus the 1961-1990 baseline, the long-term annual trend, and the region's rank in the historical record. The headline panel also shows the long-term trend rate per decade and the warmest and coolest years on file.
Where does the climate data for US Southwest come from?
Climate data for US Southwest comes from authoritative climate datasets including national meteorological services and peer-reviewed reanalyses, refreshed every month, when the upstream temperature and rainfall data are refreshed.
What is the climate baseline used on this page?
Anomalies on this page are calculated against the 1961-1990 climatological baseline, which is the standard reference period used by the Met Office, NOAA, IPCC and most national climate services. Some panels also show the source-native 1901-2000 (NOAA) or 1991-2020 (WMO) baselines for verification. See Methodology & Sources for the full reference.
Which areas does the US Southwest climate data cover?
The US Southwest climate profile covers Arizona, Colorado, New Mexico, Utah and surrounding areas. NOAA Southwest - AZ, CO, NM, UT
How often is the US Southwest climate update refreshed?
The US Southwest climate update is refreshed monthly, typically a few days after the previous month closes and the upstream provider (Met Office HadUK-Grid, NOAA Climate at a Glance, Copernicus ERA5 or the Global Carbon Project) publishes its update. See the Climate Rankings for cross-region comparisons.
What counts as a Heatwave Day on the US Southwest climate page?
Heatwave Days use the Warm Spell Duration Index (WSDI) - the WMO/ETCCDI-standard heatwave measure: days that are part of a run of 6 or more consecutive days above the local 90th-percentile temperature for that calendar day. The 90th-percentile threshold varies by time of year (a hot day in January is judged differently to one in July) but is fixed to the 1961-1990 baseline for every year shown - it does not shift as the climate warms, which is why Heatwave Days trend upward over time.
Does the US Southwest climate page include frost and snow data?
Yes. Frost Days (days with a minimum temperature below 0°C, World Bank CCKP) and snow water-equivalent (GPCC) are shown alongside temperature and precipitation, each measured against the 1961-1990 baseline where a like-for-like historical comparison is available.