The hazardous season in the United States is the time of year between roughly May and October when a number of climate-related hazards often occur, including heat waves, floods, wildfires and hurricanes — sometimes simultaneously or back-to-back. Due to climate change, many of these events are more frequent, more intense and/or longer lasting, and as a result more and more communities are at risk of damage.
We’re four months into the dangerous season and have another two months to go before the season *hopefully* begins to wind down. My colleagues and I have been monitoring extreme weather every day since May. We’ve been tracking the number and location of extreme heat, flooding, hurricanes and wildfires issued by the National Weather Service (NWS) across the country to inform the public about what to do and keep us safe. What has Danger Season brought this year so far?
I’m sure you’ve seen enough coverage of—or experienced—the brutal heat that has hit the US this year. In large urban areas, smaller rural communities, and many places in between, episodes of extreme heat during the dangerous season put a very large portion of the population at risk. In fact, 85 percent of U.S. counties — nearly all counties in the lower 48 states — have experienced at least one heat advisory since Danger Season began on May 1.
And many counties experienced high heat conditions for many days: 1,569 counties, or about half of all counties in the contiguous United States, had warnings for at least seven days, though those days were not necessarily consecutive. For example, in early June, thousands of people in Madison, WI, endured temperatures in the upper 90s without power or air conditioning after thunderstorms knocked out power lines.
From the map below, we can see that the areas with the highest number of heat warning days are in the southern Great Plains and the Southeast. 107 counties in five states (AR, LA, MS, OK and TX) in these regions had heat advisories for 28 days or longer. Again, these weren’t necessarily consecutive days, but consider that roughly four months into the dangerous season, these counties were under a high heat warning for about a month!
Between May and July, both maximum (daytime) and minimum (nighttime) temperatures in many counties in the lower 48 states were well above the historical average, and in some cases, the temperatures were the warmest on record. in 1895, as you can see in the NOAA climate summary maps below. With these warmer than average temperatures, it’s no wonder we’re seeing so many heat advisory days.
As of May, when the 2022 hazard season began, nearly half of all counties in the continental U.S. (49.1 percent) were under at least one flood warning issued by the local NWS office. 158 of all counties in the lower 48 states experienced flood warnings for seven or more days, though not necessarily consecutively. While this is only 5.1 percent of all counties, it is likely an underestimate of flood risks this year because we began monitoring in May, well after the spring flood season typically begins.
Some regions recorded a very high number of flood days. For example, Woodruff County (AR), Crow Wing County (MN), Sanborn County (SD), and Catron County, Los Alamos County, Mora County, and Sandoval County (all in NM) were on alert between the 22nd and 33rd — that means 3 to 4 weeks of flood warnings from May.
The combination of high temperatures, very low humidity and strong winds can increase the risk of fire. The National Weather Service issues a “red flag” warning when these conditions occur.
So far this dangerous season, 511 counties (or 16.5 percent) in the lower 48 states have been under at least one fire alarm. The land area in these counties is nearly 3 million square kilometers, meaning about 40 percent of the total land area in the contiguous United States was under at least one fire warning as of the start of the 2022 hazard season. 22 counties have had between 15 and 23 weather warnings (or 2-3 week warnings) since then.
For example, in New Mexico, where most counties had between 8 and 14 days of fire warnings, wildfires have increased since the mid-1980s. Across the western U.S., warming associated with human-induced climate change over the past 40 years is one reason the region has seen an increase in the size of wildfires. Growing wildfires are threatening human lives, water resources, and transportation and housing infrastructure, as well as increasing the risk of mudslides and flash floods.
Concurrent extreme weather events
During the Danger Season, episodes of extreme heat, flooding and wildfires can occasionally occur simultaneously or back to back.
While we didn’t evaluate how the current occurrence of heat, flood and wildfires changed from the historical average during this year’s hazard season, we did look at the frequency of those three types of warnings in counties during the same week. . Having to deal with at least two extreme events between floods, heat and fires in short time frames increases the health risks for the affected population and first responders.
At the beginning of August, for example nine Kentucky counties were severely affected by flooding that resulted in a FEMA disaster declaration; the following week, those counties were under a NWS heat warning as the heat index reached the 95°F-100°F range.
So far during the dangerous season, 116 counties in the Great Plains, Southwest and Northwest have been under multiple types of warnings in the same week. Of these, 83 districts had simultaneous fire and heat warnings, 18 had flood and heat warnings, and 15 had fire and flood warnings.
Our first snapshot of the dangerous season
The results in this post are from this year’s Danger Season image and we do not have matching images from previous years. But we do know this: in many areas where there have been a large number of heat warnings since the start of the dangerous season, the number of days with high temperatures is high.
For example, in July 2022, Tulsa, OK recorded 20 days with maximum temperatures above 100°F, and the next higher number of such days, 26, occurred in 2011.
The Dallas/Fort Worth area similarly had 27 days above 100°F, and a similar number (30) was also last seen in 2011 (see methods description at the end of this blog post for sources).
While these results certainly paint a picture of a country struggling through a summer of climate extremes, they can’t tell us for sure if and how this year is exceptional due to human-caused climate change.
How do these results compare to the historical number of heat index days above 100°F in UCS’s 2019 Killer Heat analysis? The frequencies of heat warnings and days above 100°F are comparable for most regions, except for the Pacific Northwest and Northeast. By mid-century, we can expect even more frequent heatwaves, as the number of days above 100°F is projected to exceed the number of heat warnings in most places.
It’s important to note that heat and other extreme weather warnings from the NWS are an imperfect way to track risks over the course of a season or over many years. The criteria for issuing alerts can change over time, making comparisons from year to year difficult. And the authorities that issue these alerts also use some local discretion to determine if and when an alert is necessary.
For example, a 95°F day in early May, when local populations are not yet seasonally acclimated to high temperatures, may warrant a warning, while the same conditions in mid-August, when people have several months to acclimate to the warm season, may not. However, the frequency of warnings this year can give us an idea of how often conditions have crossed the threshold of being potentially harmful to human health and lives.
We need to act to protect vulnerable people from the very real threats of a dangerous season, for example by giving them access to cooling and creating incentives for clean energy-powered residential electrification. Congress must pass both the National Climate Adaptation and Resilience Strategy (NCARS) Act so that there can be a plan to manage the combined risks, and the Asunción Valdivia Heat Illness and Mortality Prevention Act to protect outdoor workers from extreme heat. And the recently signed Inflation Reduction Act, while containing provisions that could increase the damage frontline communities face from fossil fuel pollution, will otherwise be a big step forward in electrification, environmental justice and climate resilience.
The dangerous season will continue to threaten our lives and well-being, and we must act now to avoid the worst climate impacts.
Access to the data and supporting information can be found here.
Originally published by the Union of Concerned Scientists, The Equation.
Juan Declet-Barreto, Chief Social Scientist for Climate Vulnerability
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