Memorial weekend saw extreme heat across a large portion of the State of Texas. My family was scheduled to go camping and hiking Sunday and Monday at Enchanted Rock. We chose Memorial Day weekend for the outing because that is early enough in the summer that our family of experienced campers can usually handle the upper eighties and low nineties we often see this time of year.
The reason I was particularly aware of the potential for extreme heat is because of a new product the National Weather Service is using this year called the Heat Risk Index. This is an experimental tool to help people plan ahead for the possibility of extreme heat. It incorporates variables like temperature and humidity and produces a graphic that indicates the level of risk.
This is going to be a useful tool going forward for people responsible for planning outdoor activities and for city personnel planning when to activate cooling centers for people without access to air conditioning.
But this Memorial Day Weekend forecasters called for unseasonably hot temperatures paired with unusually high humidity.
The intense heat Texas experienced over Memorial Day Weekend was caused by the northern extent of a strong high pressure system that has been sitting over northern Mexico for some time now. Ridges of high pressure tend to stay in one place for weeks, blocking large-scale storm systems and inhibiting cloud development. They also create hot conditions because of gently sinking air that compresses and warms as it reaches the surface.
In Texas, we are used to seeing that kind of hot high pressure system later in the summer when a semi-permanent ridge of high pressure sets up over the central United States. You may have heard it called the “Death Ridge.” The Death Ridge is the culprit for those long weeks of high temperatures in the upper nineties and low one hundreds we see in July and August.
The high humidity that made this heat wave even more unpleasant came from the very warm Gulf of Mexico. When the water in the Gulf of Mexico is very warm, water evaporates easily, which leads to high humidity in adjacent areas like Texas. In Austin, the dewpoint, a measure of the humidity in the air, on Monday was an unreal seventy-eight degrees. Paired with an air temperature in the upper nineties, that is some dangerous heat.
The heat index is the measure meterologists use to estimate the effect of the combined air temperature and humidity has on how hot the weather feels. Houston Hobby Airport recorded a heat index of 115 degrees Fahrenheit on Monday, which according to Space City Weather, is the hottest heat index recorded in May in Houston, ever.
The combination of heat and humidity is especially harmful to living things. Our bodies depend on the evaporation of sweat to keep our temperature in a safe range. When the humidity is high, sweat can’t evaporate as efficiently and heat stays trapped in the body. That can lead to heat stress, including heat exhaustion and heat stroke, which can be fatal.
During heat advisories, officials recommend avoiding outdoor exertion, taking breaks in the shade, and drinking plenty of water. If you have access to air conditioning, it is recommended that you avoid the outdoors during the hottest part of the afternoon.
A particularly worrying part of the increase in very hot weather driven by climate change is the increase in overnight low temperatures. When overnight lows don’t fall below eighty degrees Fahrenheit, the body has no opportunity to rest from the heat during the nighttime hours. That means that heat stress compounds day after day. This is a major concern for people who don’t have access to air conditioning and is the reason cities open cooling shelters when conditions are as hot as they were over the weekend.
Texas has always had hot summers, but it may seem like recent summers have been worse than before. The Office of the State Climatologist projects that as the climate changes in response to human emissions of greenhouse gases, the yearly average temperature in Texas is projected to be three degrees Fahrenheit higher than the average from 1950-1999.
That higher average temperature means extreme temperatures are more likely. Texas can expect double the number of days with temperatures over one hundred degrees Fahrenheit when compared with the yearly average in the period from 2001-2020, with additional very hot days expected in urban areas.
After my family made significant changes to our camping plans in response to the extreme heat this weekend it was clear that we are now in a climate where we need to start accounting for dangerous heat when planning things like Scout campouts and hikes the same way we account for thunderstorms and freezing temperatures. In the past planning for water and breaks was enough. Now those who plan outdoor events must consider thresholds for the heat index above which we cancel outdoor practices and activities. Now we should make a plan for access to air conditioning during outdoor activities.
Increased heat waves, increased humidity, and prolonged periods of temperatures exceeding the century mark are concerning projections for Texas in a warming climate. Many of the social and cultural events that we look forward to in the summer months are threatened by extreme heat. The Hartmann Concerts in the Park outdoor concert series at the Long Center in Austin had to cancel multiple dates in a row last summer due to unsafe heat conditions.
Festivals like Austin City Limits depend on safe outdoor conditions to bring thousands of people and musicians to the city every year. Outdoor restaurants and clubs, sports leagues for people of all ages, and our beautiful park and trail systems all reflect a culture of enjoying the outdoors that is at risk as the climate warms.
Paired with the danger posed to vulnerable populations like those who live or work outside, extreme heat is a major reason Texans should support robust policy aimed at mitigating climate change at all levels of government.