Until recently, the hottest month on record for USA48 (a.k.a. the “lower 48 states” of the USA) was July 1936, with two of the five hottest months from the 1930s (the “dust bowl” era). Not any more. According to data from NOAA, we just set a new record; now the hottest of all is July 2026, and four of the five hottest are after the year 2000. In the following graph, this July is circled in red:

Perhaps of greater interest, at least scientifically, is the trend in USA48 temperature, which is clear from yearly average temperature anomaly (the last value is year-to-date for 2026):

The average warming rate since 1975 is 0.31 ± 0.09 °C/decade (0.56 ± 0.16 °F/decade, intervals are ± 2σ), which is more than 50% larger than the global average rate.

Climate change hasn’t had the same affect on every part of the country. For one thing, we’re not warming at the same rate nationwide. I computed the warming rate since 1975 for each state; here’s a plot with blue dots for cooling states (there aren’t any) and red dots for warming states, with larger dots for faster rates:

All states are warming, but at visibly different speeds. North Dakota has been slowest to heat up at 0.35 ± 0.38 °F/decade (I’ll use degrees Fahrenheit for the remainder of the post), about equal to the global average during the same time period, and for this state the 2σ uncertainty is larger than the estimate itself. New Mexico is fastest-warming at 0.74 ± 0.17 °F/decade, twice the global average. Here’s the same graph, but with blue dots for states warming slower-than-average, red dots for those faster-than-average, and larger dots for greater difference from the USA48 average:

Clearly the slowest-warming states are in the north: the Dakotas, Iowa, and Washington state. Fastest-warming are southwest states: New Mexico, Texas, Arizona, and Utah.

When it comes to public perception of climate change, I believe that not all warming rates are created equal, that what people notice most is daily high temperature during summer. Here’s the warming speed (since 1975) for the 48 states for high temperature during summer (June/July/August), which shows warming strongest in the western U.S., less in the Northeast, and almost nonexistent in a large swath of the central part of the USA:

This is part of the reason western states are suffering the worst heat wave problems. But we can’t ignore night-time warming, which can make heat waves so much more deadly. Which warms faster, days or nights? We can tell from the trend in the diurnal temperature range (DTR), which is upward when days warm faster, downard when nights warm faster. Here are trends in DTR for each state, in red for faster warming during the day, blue at night; in most western states, warming days dominate nights, but in most of the eastern states the night dominates day.

One of the things most responsible for this difference between the two halves of the country, is that in the west precipitation is declining, while it is increasing in the east. Here’s the trend (since 1975) in annual precipitation for each state, where red dots show decrease and blue dots increase:

The midwest is getting more, the southwest less, and that (as well as the heat) is why drought (as estimated by PDSI, the Palmer Drought Severity Index) is getting worse in the western USA, but not so in the east. Here’s the trend in PDSI, red for more drought, blue for less:

Based on all these quantities, I’ll split the lower 48 states into two groups, the “West” and “East.” The west consists of twelve western states: Texas, New Mexico, Arizona, California, Nevada, Utah, Colorado, Wyoming, Montana, Idaho, Oregon, and Washington. The east is the remaining states. The west is getting most of the attention these days, because greater warming, especially during daytime during summer, makes for more intense heat waves, and because drier conditions have made drought worse. That leads to a lot of problems, including the crisis in water availability for the Colorado River basin and an explosion of wildfire this year in western states.

However you look at it, the impact of changing climate has not been the same nationwide, nor will it be in the future.

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