We have a new term to add to our lexicon of extreme weather phenomena: thirstwave. In a report published last month (April 2025) in “Earth’s Future,” researchers Mike Hobbins and Meetpal Kukal introduced the term thirstwave to describe an extended period of intense evaporative demand or atmospheric thirst. Evaporative demand is a scientific measurement of potential evaporation of water from the earth’s surface and is influenced by temperature, wind speed, humidity and solar radiation or sunshine. Thirstwaves are characterized by periods lasting 3 days or longer when the evaporation rate exceeds 90 percent of normal.
Hobbins works for NOAA’s Physical Sciences Laboratory at the Cooperative Institute for Research at the University of Colorado (CIRES) and Kukal works at the University of Idaho as a research hydrologist. Their research shows that our atmosphere is getting thirstier. Not just drier and hotter during heat waves and heat spikes, but at times the atmosphere itself is actually drawing or pulling more moisture directly out of the soil and plant tissues.
Hobbins and Kukal’s longitudinal study shows that, from 1980 to 2021, thirstwaves occurring in the contiguous United States became more frequent and more intense. According to an article by Jack Lee published on April 20, 2025, in the San Francisco Chronicle, of the 30 counties with the highest frequency of thirstwaves during the 1981-2021 growing seasons, nine were in California, with 47 of 58 California counties recording statistically significant increases in the frequency of thirstwaves annually.
Hobbins and Kukal prepared a color-coded map of the United States which was printed along with the article in the Chronicle showing the average annual frequencies of thirstwaves by county in each state. The frequencies of thirstwaves in Fresno and Madera counties are among the highest, with an average of 3.5 to 4 occurrences annually.
As research continues into thirstwaves, scientists will undoubtedly begin to focus on efforts to mitigate the serious effects. Soon, we may see weather forecasters include thirstwaves in their forecasts. In the meantime, how can Central Valley gardeners best prepare for thirstwaves? Since thirstwaves suck moisture out of the soil and plant tissues, mitigation of damage begins with intensifying efforts to slow evapotranspiration rates.
Mulches are one of the best methods of slowing evaporation of moisture from the soil. Adding large amounts of organic material to the soil really does improve the soil’s ability to retain water. Irrigation techniques will need to be improved and revamped. Central Valley gardeners have learned that on hot summer days water delivered from overhead sprinklers can evaporate into the air before it touches the ground. Regular deep, slow irrigation to thoroughly soak root systems during the summer should become the norm. And when high temperatures are predicted to occur at the same time as dry winds and intense sun rays, the ideal conditions for the development of thirstwaves, all plants and trees should be deeply irrigated before, during and after the event.
Sources:
Jack Lee, ’Thirstwaves and agricultural threat, fire risk’, San Francisco Chronicle, April 20, 2025
M.S. Kukal and M. Hobbins, Advancing Earth and Space Sciences journal, ‘Earth’s Future’, Vol. 13, Issue 3, March 20, 2025,
Muhammed Tuhin, ‘Thirstwaves: A New Climate Threat to Agriculture’, Science News Today, April 8, 2025
Sanjana Gajbhiye, 'Thirstwaves: The hidden climate threat drying out American farms,” Earth.com.
‘Researchers coin ‘thirstwaves’ as new term for prolonged periods of atmospheric thirst,’ cires.colorado.edu/news, March 20, 2025
________________________
Written by UC Master Gardener Elinor Teague.