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In January 2025, 166 out of 191 analyzed U.S. cities were cooler than normal, with the Ohio Valley and Southeast particularly affected. Despite these cool anomalies, no city set a low temperature record for January, and the warming influence of climate change remained pronounced. Alaska was the warmest state, with Fairbanks recording the highest anomaly at 14.6°F above normal. Analysis using the Climate Shift Index (CSI) showed that days where warmer temperatures were made at least twice as likely by climate change outnumbered days where cooler temperatures were made twice as rare.

The analysis finds that human-caused climate change has significantly increased the frequency of dangerous nighttime temperatures globally, affecting billions of people. Using the Climate Shift Index, the report quantifies additional nights above 18°C, 20°C, and 25°C, noting that these temperatures disrupt sleep and increase risks of cardiovascular conditions and mortality. The most severe impacts are observed in tropical regions and urban areas due to heat island effects, with specific cities in India, Indonesia, and Africa experiencing an additional month or more of extreme nighttime heat.

The report finds that July 2024 temperatures were elevated in the eastern and western thirds of the United States, with the West Coast showing particularly high anomalies. Using the Climate Shift Index (CSI), the analysis identifies the Southwest as having the strongest climate signal, with cities averaging at least 14 days where temperatures were at least three times more likely due to climate change. Specific cities like Spokane, Washington, and Reno, Nevada, showed significant temperature anomalies and long-term warming trends since 1970.

The period from November 2022 to October 2023 was the hottest 12-month stretch in recorded history, with a global average temperature 1.32°C above the pre-industrial baseline. Using the Climate Shift Index (CSI), Climate Central found that 90% of the global population (7.3 billion people) experienced at least 10 days of temperatures very strongly affected by climate change (CSI level 3 or higher). Approximately 1.9 billion people (24%) experienced a five-day heat wave strongly influenced by carbon pollution (CSI level 2 or higher). The report highlights an inequitable distribution of impacts, with small island developing states and least developed countries facing higher exposure, although heat waves also occurred in G20 nations. The analysis also links human-induced climate change to severe weather events, including deadly flooding in Africa and Libya, and record-breaking wildfires in Canada and Hawaii.

Climate Central analyzed temperature data from 244 U.S. cities to determine the increase in days falling within the 61-93°F range suitable for disease transmission by Aedes and Culex mosquitoes. The analysis found that 94% of these cities are experiencing an increase in these 'disease danger days' since 1970, with significant increases noted in California, the Southwest, and some northern cities. While most areas face higher risks, some locations like Phoenix may become too hot for mosquito survival. The report also highlights that warmer temperatures shorten the Extrinsic Incubation Period (EIP) of viruses, potentially increasing the number of infectious mosquitoes and expanding the range of species like Aedes albopictus.