2021 record rain days

Key concepts

• 72% of 246 locations evaluated have seen an increase in the amount of rain falling on their annual wettest day since 1950, especially in the Gulf Coast and Mid-Atlantic.
• A broader analysis of 2568 stations shows that, in 2021, 15% had one of their top ten annual wettest days on record. Thirty-seven of those sites took the top spot.
• A warmer atmosphere can hold more moisture, increasing the potential for heavier downpours. 
• Flooding and mudflows brought by heavy rains can cost billions in damages, threaten public health, and exacerbate racial and socioeconomic inequities.

Some of the heaviest rains have been getting heavier since 1950

• Climate Central found that 72% (178) of 246 locations analyzed have seen an increase in the amount of rain falling on their annual wettest day since 1950.
• Locations along the Gulf Coast and Mid-Atlantic have experienced the greatest increase by volume in their heaviest rainfall events. Houston tops the list with 2.8 additional inches on its annual wettest day compared to 1950, or an 83% increase. This is followed by Greenville, N.C., Pensacola, Fla., Hattiesburg, Miss. and Baton Rouge, La.
• These trends are consistent with long-term increases in the  amount of precipitation falling in the heaviest one percent of downpours across the country, with the largest increases in the northeastern U.S.

2021 has been a record-breaking year for extreme rainfall events from coast to coast

• For 15% of 2568 stations evaluated across the contiguous U.S., their wettest day of 2021 ranks in their top-ten annual wettest days on record.
• Through the end of October, 37 of these locations (including Sacramento, Calif., Newark, N.J. and La Crosse, Wis.) experienced their wettest day since 1950. 
• Record-setting rainfall in the Northeast looks different than in the more arid West. For example, Sacramento’s record-setting 5.4” downpour on October 24th accounted for 48% of the city’s year-to-date rainfall, while Newark’s record-setting 8.4”on September 1st comprised only 16% of the city’s year-to-date rainfall.

Rising temperatures and extreme rainfall are linked

• A warming world leads to more-intense periods of both extreme rainfall and drought because higher temperatures lead to greater evaporation from land and sea. 
• For every 1°F increase in temperature, the atmosphere is able to hold about four percent more moisture, leading to more frequent and intense heavy rain events. 
• The frequency and intensity of heavy rainfall events are projected to increase with additional warming over this century. 

Heavy rains bring many risks, including flooding and mudflows—even in the driest places. 

• Economic loss: Flooding is one of the costliest weather-related hazards in the U.S., causing $43 billion in damages over the last five years (2016-2020). Precipitation extremes are estimated to be responsible for over one-third of flood damages. Damage to croplands and critical infrastructure during 2019 flooding in eight states along the Missouri River totaled $11.6 billion, becoming one of the most expensive inland flooding events on record. 
• Threats to public health: Floodwaters can expose individuals to toxic contaminants, water-borne diseases, and dangerous debris. Tennessee floods in August 2021 resulted in over 20 drowning deaths. Exposure to hazards like flooding, mudflows, and extreme precipitation have been linked to increased post-traumatic mental disorders. 
• Social disruption: Downpours can displace families from their homes, compromise agricultural economies by drowning crops, and prevent access to public services like healthcare and education. The consequences of flooding are exaggerated in poor, rural, and redlined—traditionally, Black and Brown—communities through neglected infrastructure and discriminatory housing and relief policies. The financial and psychological burdens of flood exposure complicate the pursuit of recovery and social mobility.