11. West Coast of the U.S.: California
In February of 2019, record-setting levels of rain in California led to floods throughout the northern part of the state. Scientists predict that extreme precipitation events will continue to increase in intensity in California in the future, as well as greater variability between wet and dry years — meaning more droughts and more floods. One study published in the May 2018 edition of the peer-reviewed journal Nature Climate Change found that wet extremes in California will increase by 100% to 200% by 2100.
12. Western U.S.: Colorado, Utah, California
Snowpack in the western states was dramatically lower in the winter of 2017-18. By mid-February, statewide snowfall had fallen to 49% of normal in Utah, and 85% below average in Colorado. According to the National Climate Assessment, the reduced snow levels are part of a larger trend of declining winter snowpack throughout the southwestern United States over the last 50 years, due largely to warmer temperatures that cause precipitation to fall as rain rather than snow and cause existing snowpack to melt earlier in the year.
Snow drought can lead to reduced water availability in the summer and have negative impacts on economies that rely on outdoor tourism and recreation. Snow drought can also have other impacts on people, agriculture, and wildlife.
13. Western U.S.: California
For the first time in over seven years, California was officially declared free of drought in March 2019. The drought led to major losses in the California agricultural sector, significant environmental damage, and water shortages in some rural areas. Many scientists have concluded that human-induced climate change has substantially increased the likelihood of extreme droughts in California, and contributed to the state’s most recent drought emergency.
14. Western United States
After historic amounts of rain fell in the winter of 2016-17 and snowpack level rose, much of the western United States experienced an early spring melt, leading to increased risk of flooding and dangerous fluctuations in river flow. The faster snowmelt is partially the result of warmer temperatures earlier in the year, causing spring conditions to arrive as much as 20 days earlier than normal in some parts of the country. Scientists say because of human-caused climate change, spring is beginning about 2.5 days earlier every decade on average.
15. Western United States
According to the Third U.S. National Climate Assessment, heat waves in the United States have become more frequent since the 1960s, while the frequency of cold waves has declined. The annual average temperature over the contiguous United States has risen 1.8 degrees from 1901 to 2016 and is projected to increase an additional 2.5 degrees from 2021 to 2050.