As the average temperatures rise, the average number of hot days (> 90°F) per year is projected to increase 12-20 days by 2050.
By mid-century, Missoula County’s average annual temperature is projected to increase by about 3-5°F, with the greatest temperature increases projected to occur in July, August, and September.
Explore how higher temperatures create vulnerabilities in the following sectors given climate change:
AGRICULTURE.
Warmer weather will have some positive impacts on Missoula County’s agricultural sector by increasing the length of the growing season (later fall freeze and earlier spring thaw), creating opportunities for new crops such as stone fruits, grapes, melons, and corn. The longer growing season may also increase revenues for alfalfa and hay producers by allowing for additional cuttings during the growing season. Missoula County agricultural producers report that there is already a shortage of farm labor during the growing season, and a longer season may make this challenge more acute by increasing labor needs.
However, hotter summers will make outdoor working conditions more difficult for farmers and ranchers, particularly in combination with increased wildfire smoke. Heat can also stress crops and reduce yields, particularly for cool weather crops such as spinach, lettuce, and peas. Heat stress on livestock affects animal growth and reproduction and can inflict heavy economic losses on ranchers. Milder winters can encourage the proliferation of pests and diseases that affect crops. Heat also exacerbates the impacts of drought and drier summers on agriculture by increasing evapotranspiration rates.
The full vulnerability grid for Agriculture, for all hazards, is shown below.
However, hotter summers will make outdoor working conditions more difficult for farmers and ranchers, particularly in combination with increased wildfire smoke. Heat can also stress crops and reduce yields, particularly for cool weather crops such as spinach, lettuce, and peas. Heat stress on livestock affects animal growth and reproduction and can inflict heavy economic losses on ranchers. Milder winters can encourage the proliferation of pests and diseases that affect crops. Heat also exacerbates the impacts of drought and drier summers on agriculture by increasing evapotranspiration rates.
The full vulnerability grid for Agriculture, for all hazards, is shown below.
aquatic systems.
Higher air temperatures lead to higher water temperatures and increased evapotranspiration, exacerbating lower summer streamflows caused by earlier spring runoff (see Drought and Drier Summers section). Higher river temperatures will force temperature-sensitive species like bull trout and cutthroat trout to move upstream to cooler water, shrinking the size of their habitat.
Hotter summers and decreased streamflows will cause some smaller streams to dry up altogether for part of the year, increasing stress on riparian vegetation and aquatic species. With vegetation loss comes reduced shading of the stream, resulting in even higher water temperatures and further reducing water levels. Loss of riparian vegetation can also lead to increased hillslope runoff and erosion.
Hotter summers will increase demand for water-based recreation, with the potential for increasing stress on aquatic plants and animals. For example, heavy use often results in the creation of unofficial river access trails, resulting in decreased vegetation and increased erosion. This is an ongoing problem on the Clark Fork River in Missoula and has the potential to worsen with increased river recreation.
The full vulnerability grid for Aquatic Systems, for all hazards, is shown below.
Hotter summers and decreased streamflows will cause some smaller streams to dry up altogether for part of the year, increasing stress on riparian vegetation and aquatic species. With vegetation loss comes reduced shading of the stream, resulting in even higher water temperatures and further reducing water levels. Loss of riparian vegetation can also lead to increased hillslope runoff and erosion.
Hotter summers will increase demand for water-based recreation, with the potential for increasing stress on aquatic plants and animals. For example, heavy use often results in the creation of unofficial river access trails, resulting in decreased vegetation and increased erosion. This is an ongoing problem on the Clark Fork River in Missoula and has the potential to worsen with increased river recreation.
The full vulnerability grid for Aquatic Systems, for all hazards, is shown below.
buildings and landscaping.
Many homes, schools, and other public and commercial buildings in the county are ill-prepared for extreme heat (i.e. poorly insulated, lacking awnings, not air conditioned), so hotter temperatures will lead to diminished quality of life for building occupants.
Heat also degrades building components and accelerates the growth of mold and insect infestations (e.g. termites and cockroaches), all of which decrease the useful life of the building. Heat can kill urban trees, shrubs, and other plants, especially when combined with less summer precipitation and lack of adequate irrigation. Fewer trees and plants in the urban area decrease shading and exacerbates the urban heat island effect.
Building design and quality, particularly housing, can exacerbate the health effects of heat and smoke events. People living in poor-quality housing may experience increased heat stress, and the people living in the poorest quality housing often have more limited resources to respond to these stresses.
The full vulnerability grid for Buildings and Landscaping, for all hazards, is shown below.
Heat also degrades building components and accelerates the growth of mold and insect infestations (e.g. termites and cockroaches), all of which decrease the useful life of the building. Heat can kill urban trees, shrubs, and other plants, especially when combined with less summer precipitation and lack of adequate irrigation. Fewer trees and plants in the urban area decrease shading and exacerbates the urban heat island effect.
Building design and quality, particularly housing, can exacerbate the health effects of heat and smoke events. People living in poor-quality housing may experience increased heat stress, and the people living in the poorest quality housing often have more limited resources to respond to these stresses.
The full vulnerability grid for Buildings and Landscaping, for all hazards, is shown below.
emergency preparedness and response.
As extreme heat contributes to and exacerbates health problems, emergency personnel will need to respond to more emergencies. This will require more emergency planning and communication and will further stress the limited resources of Missoula County’s emergency services, especially when extreme heat coincides with other extreme events like wildfires. Emergency personnel who are active outdoors are also vulnerable to heat-related illnesses.
The full vulnerability grid for Emergency Preparedness and Response, for all hazards, is shown below.
The full vulnerability grid for Emergency Preparedness and Response, for all hazards, is shown below.
energy.
Hotter summers will increase the demand for air conditioning, leading to increased energy bills for residents and businesses and to an increased overall demand for electricity during hot hours. This has the potential to increase utility costs to supply this increased ‘peak load’, ultimately leading to even higher costs for utility ratepayers. Additionally, extreme heat can decrease the effectiveness of power lines and other electrical equipment, potentially leading to blackouts during very hot conditions.
The full vulnerability grid for Energy, for all hazards, is shown below.
The full vulnerability grid for Energy, for all hazards, is shown below.
forests and terrestrial ecosystems.
Increasing temperatures will likely increase the spread and impact of forest pathogens including fungi and insects. Warmer winter temperatures, in particular, are likely to allow mountain pine beetles and other bark beetle species to proliferate across Missoula County and expand their range to higher elevations. If continued large-scale bark beetle outbreaks occur, this, along with reduced regeneration due to climate change, is projected to lead to a substantial decline in the area covered by forest in Missoula County.
Warmer temperatures also have the potential to alter basic phenological processes that result in mismatches between species. For example, the timing of host plant flowering and pollinator activity may be out of sync, and changes in the timing of plant growth may affect foraging animals. Plant and animal species better adapted to warmer temperatures may outcompete local species, especially as other climate impacts continue to displace native flora and fauna.
The full vulnerability grid for Forest and Terrestrial Ecosystems, for all hazards, is shown below.
Warmer temperatures also have the potential to alter basic phenological processes that result in mismatches between species. For example, the timing of host plant flowering and pollinator activity may be out of sync, and changes in the timing of plant growth may affect foraging animals. Plant and animal species better adapted to warmer temperatures may outcompete local species, especially as other climate impacts continue to displace native flora and fauna.
The full vulnerability grid for Forest and Terrestrial Ecosystems, for all hazards, is shown below.
human health.
Hotter summers increase the risk of heat stress and heat-related cardiac issues (heart attack and stroke), particularly among older adults, outdoor workers, people without access to cool indoor spaces, and people with chronic health conditions. These risks are exacerbated in the urban area since buildings and paved surfaces heat up faster than natural landscapes. This is known as the ‘urban heat island’ effect. The urban heat island effect can be exacerbated by increased use of air conditioners, since air conditioners release heat from inside buildings to the outdoors. In addition to high temperatures during the day, those without air conditioning may suffer from sleep deprivation as average nighttime temperatures increase.
Wildfire smoke combined with heat can be particularly problematic, since smoke discourages people from opening windows at night to cool their homes. Sleep loss can cause a range of health problems, including a weakened immune system. High temperatures can discourage exercising, and in some cases make outdoor exercise inadvisable. This has worrying implications for physical health and obesity rates, particularly among people who lack the resources to find indoor places to exercise. On the other hand, warmer springs, summers and falls may result in Missoula County residents spending more time outdoors, resulting in increased rates of skin cancer. Montana already has higher than the national average rate of skin cancers.
Extreme heat, especially for long periods of time, also negatively impacts mental health. An inability to escape the heat can lead to or exacerbate multiple mental health conditions, including anxiety, depression, and substance abuse. In addition, extreme heat can lead to social isolation, even for those with the ability to escape the heat. Rural residents, the elderly, those with existing mental health conditions, and mobility challenged individuals are particularly vulnerable to increased social isolation as a result of extreme heat. Aside from extreme heat, there is evidence to suggest that warmer weather across all seasons may increase rates of violent crime.
The full vulnerability grid for Human Health, for all hazards, is shown below.
Wildfire smoke combined with heat can be particularly problematic, since smoke discourages people from opening windows at night to cool their homes. Sleep loss can cause a range of health problems, including a weakened immune system. High temperatures can discourage exercising, and in some cases make outdoor exercise inadvisable. This has worrying implications for physical health and obesity rates, particularly among people who lack the resources to find indoor places to exercise. On the other hand, warmer springs, summers and falls may result in Missoula County residents spending more time outdoors, resulting in increased rates of skin cancer. Montana already has higher than the national average rate of skin cancers.
Extreme heat, especially for long periods of time, also negatively impacts mental health. An inability to escape the heat can lead to or exacerbate multiple mental health conditions, including anxiety, depression, and substance abuse. In addition, extreme heat can lead to social isolation, even for those with the ability to escape the heat. Rural residents, the elderly, those with existing mental health conditions, and mobility challenged individuals are particularly vulnerable to increased social isolation as a result of extreme heat. Aside from extreme heat, there is evidence to suggest that warmer weather across all seasons may increase rates of violent crime.
The full vulnerability grid for Human Health, for all hazards, is shown below.
land use planning and transportation.
Buildings and paved surfaces contribute to the urban heat island effect, making the Missoula urban area hotter than rural parts of the county. Missoula City and County zoning codes include requirements for off-street parking that have the potential to exacerbate the urban heat island effect by increasing impermeable paved area. Land use planning and transportation also affect housing affordability and quality, and hence the building and health impacts of high temperature events.
The full vulnerability grid for Land Use Planning and Transportation, for all hazards, is shown below.
The full vulnerability grid for Land Use Planning and Transportation, for all hazards, is shown below.
water infrastructure.
Higher temperatures will increase evapotranspiration rates across Missoula County, increasing the demand for irrigation. Covenants that require turf grass limit homeowners’ flexibility to convert to less water-intensive landscaping. Increased evaporation will also reduce surface water stored in reservoirs. While most of Missoula County relies on groundwater, this will impact the community of Seeley Lake and a small number of other county residents that rely on treated surface water.
The full vulnerability grid for Water Infrastructure, for all hazards, is shown below.
The full vulnerability grid for Water Infrastructure, for all hazards, is shown below.