Res 2024-045 approving the 2024 City of San Marcos Hazards Mitigation Action Plan (“HMAP”)

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SECTION 4: RISK OVERVIEW Climate change is expected to lead to an increase in average temperatures as well as an increase in frequency, duration, and intensity of extreme heat events. With no reductions in emissions worldwide, Texas is projected to experience an additional 30 to 60 days per year above 100°F than what is experienced now.2 The State Climatologist's Assessment of Historic and Future Trends of Extreme Weather in Texas, 1900-2036 identifies ongoing and likely future trends out to the year 2036 based on analysis of historic observations of temperatures, precipitation, and extreme weather. Table 4-4 highlights future trends in extreme weather from the report. Table 4-4. Future Trends in Extreme Weather in Texas3 The average annual surface temperature in 2036 is expected to be 3.0°F warmer than the 1950-1999 average and 1.8°F warmer than the 1991-2020 average. Nearly double the number of 100°F days by 2036 compared to 2001-2020. Extreme Temperatures Higher frequency of 100°F days in urban areas. Extreme monthly summertime temperature trends imply an increase of about 1 OF compared to the 1950-1999 average. Extreme monthly wintertime temperatures are expected to continue to increase at an even faster rate. The coolest days of the summer are expected to continue becoming warmer. Precipitation has increased by 10 percent or more in eastern Texas, but little trend is present in western Texas. Precipitation trends to 2036 are likely to be dominated by natural variability. Extreme precipitation is expected to increase in intensity on Precipitation average statewide by 6-10 percent compared to the 1950- 1999 averages and 2-3 percent relative to the 2001-2020 averages. This translates to an increase in the frequency of extreme rain of 30-50 percent relative to the climatological expected frequency in 1950-1999 and 10-15 percent relative to 2001- 2020. Increasing temperatures, rainfall variability, and other factors will on balance decrease water availability, but impact Drought changes will vary strongly across applications. Impact trends to be highly sector -specific, with the impacts possibly smaller for agriculture than for surface water supply. 2 U.S. Global Change Research Program, Washington, DC, USA, pp. 987-1035. doi: 10.7930/NCA4.2018.CH23. https://nca20l8.globalchange.gov/chapter/23/ 3 Gammon -Nielsen, John, Holman, Sara, Buley, Austin and Jorgensen, Savannah. Assessment of Historic and Future Trends of Extreme Weather in Texas, 1900-2036, 2021 Update. Texas A&M University Office of the Texas State Climatologist. October 7, 2021. https://climatexas.tamu.edu/files/ClimateReport-1900to2O36-2021 Update City of San Marcos I Hazard Mitigation Action Plan Update 2024 1 Page 6