Extreme heat risks to pregnancy driven by climate change: United States

2020 to 2024

We counted the number of days with temperatures warmer than 95% of temperatures observed at a given location (also referred to as temperatures above the 95th percentile) — a threshold which research¹ shows can bring increased risk of preterm birth. We define these extremely hot days as “pregnancy heat-risk days.”

During the past five years, the U.S. experienced on average 12 additional pregnancy heat-risk days each year.
Climate change nearly doubled the average annual number of pregnancy heat-risk days experienced (12 out of 25 or 48%) in the U.S. on average each year during 2020 to 2024, compared to a world without climate change.
West Palm Beach, Florida experienced the most additional pregnancy heat-risk days each year (34) on average during the past five years (of all U.S. cities).
Utah experienced the most additional pregnancy heat-risk days each year (23) on average during the past five years (of all U.S. states).
In Honolulu, Hawaii, all of the 22 pregnancy heat-risk days experienced on average each year were added by climate change. Meaning, this city would not have experienced any pregnancy heat-risk days without the influence of climate change.*

Explore data for states and cities across the U.S. in the interactive maps below.

States with the most pregnancy heat-risk days added by climate change

Cities with the most pregnancy heat-risk days added by climate change

^*A previous version of this page incorrectly stated that in Honolulu, Hawaii, 20 out of 21 observed pregnancy heat-risk days were added by climate change. In fact, this is a statistic about the state of Hawaii and not Honolulu specifically.
¹We chose this percentile based on peer-reviewed research from Kuehn et al. (2017), Wang et al. (2013), Wang et al. (2024), and McElroy et al. (2022).