Rainfall Patterns Suppress Summer Warming in Midwest and Southeast

As of August 2025, the contiguous United States continues to experience a unique climate phenomenon known as the "summer warming hole." While global temperatures have risen significantly over the past century, with summers in the Lower 48 states now 1.6°F warmer on average than in 1896, certain regions in the central and southeastern US have bucked this trend.

In these areas, summer temperatures have actually decreased or shown only muted warming over the past 30 years compared to the early 20th century. Scientists have attributed this cooling effect to a variety of factors, including increased rainfall and the "corn sweat" phenomenon, where transpiration from crops like corn adds moisture to the air and has a cooling impact.

Reforestation in the Southeast has also played a role, as the regrowth of forests has helped draw up water through tree roots and release it into the atmosphere, creating a more humid and temperate climate. However, experts warn that this "warming hole" may not persist indefinitely, as the overall warming trend driven by climate change is expected to eventually overcome these localized cooling influences.

As one researcher noted, "If you do have a very dry year, it probably means you'll break records in maximum temperatures." The complex interplay of regional climate patterns and human-induced changes to the landscape has created this unique anomaly, which has been prominently featured in the latest US National Climate Assessment.