Duke faculty experts break down the research behind some of summer's most common questions. (Illustration by Jess Abel/Trinity Communications)
Hot Days, Cool Science: Duke Experts Break Down Summer’s Everyday Mysteries
As temperatures climb and daylight stretches late into the evening, summer brings a familiar set of experiences — buzzing mosquitoes, sun-soaked afternoons and, for many people, the urge to reset routines or chase new goals. But the season also carries serious risks. Extreme heat and wildfires can threaten lives, destroy homes and ecosystems, and send hazardous smoke across entire regions. Behind both the ordinary and unsettling aspects of summer are fascinating scientific explanations.
We asked four Duke faculty experts to break down the research behind some of the season’s most common questions — from the biology of biting insects and the physics of sunlight to the psychology of seasonal habits and the forces driving increasingly dangerous wildfires. Together, these researchers explore the science shaping how we experience summer.
Jacob Levine, assistant professor of Biology
Levine is a plant community ecologist who studies what drives wildfire severity and how management can reduce those risks. His research combines field experiments, mathematical modeling and large-scale data analysis to understand how ecosystems respond to climate change.
What’s driving the increase in extreme wildfires each summer?
The causes vary by region, but three main factors are contributing to the increase in wildfire size, severity and frequency over the past several decades.
The biggest is climate change. In many places, “extreme fire weather” — defined by high heat, low humidity and severe wind — is becoming more common, causing fires to spread faster and burn more intensely. This is an important factor in recent fires in Canada, whose smoke is currently affecting large parts of the United States.
The second is that we have changed the natural fire patterns of many ecosystems. In parts of the Western United States, for example, Indigenous burning practices were forcibly interrupted, and decades of fire suppression prevented the frequent, low-intensity fires that once cleared brush and young trees. As a result, some landscapes have accumulated more dead vegetation and denser stands of less resilient trees — fuel that can feed larger fires.
The third is forest management. In some areas, timber practices increase tree density, while prescribed burning and thinning have not been carried out at the scale needed to reduce fuels. These treatments are critical, but they have not kept pace with the problem.
Together, extreme fire weather, fuel buildup and limited risk-reduction work are driving more extreme fire behavior across much of the world.
Fischer develops advanced laser microscopes that let scientists see tiny molecular details inside materials. His methods help researchers study living tissues, analyze nanomaterials, and even look beneath the surface of historic paintings without damaging them.
How are UV rays measured, and why do UV levels spike during summer months?
Light comes in different wavelengths, measured in nanometers (nm), and our eyes interpret those wavelengths as colors. Human vision detects roughly 400 nm (which appears violet) to 700 nm (which appears red). But sunlight also includes wavelengths outside that range: infrared, with longer wavelengths, and ultraviolet (UV), with shorter wavelengths. UV light is a concern because its shorter wavelengths carry more energy and can more easily damage living tissue, including skin.
In the Northern Hemisphere, the sun is higher in the sky during summer than in winter. Before sunlight reaches the ground, it must pass through Earth’s atmosphere. Some of that light is absorbed or scattered by gases and particles — even when the sky looks clear. In summer, sunlight arrives at a steeper angle and travels through less atmosphere. That shorter journey means less light is absorbed or scattered, so more reaches the surface. The effect is especially important for UV light, which the atmosphere absorbs and scatters more readily than visible light.
Scientists measure UV — and the rest of sunlight’s spectrum — by using prisms to separate light into its component wavelengths, like a rainbow. They can also use diffraction gratings, patterned surfaces that spread light into colors — a familiar example is the rainbow seen when sunlight reflects from a CD. Sensors then measure the amount of light at each wavelength. Instruments that perform these measurements are called spectrometers or spectroradiometers.
Ke Dong, professor of Biology
Dong is an entomologist who studies how mosquitoes and other insects respond to chemicals, including mosquito repellents and insecticides. Her research focuses on the neurotoxicology and behavior of Aedes aegypti, a mosquito species that can spread diseases such as dengue, yellow fever and Zika, with the goal of improving strategies to control pathogen-carrying mosquitoes.
How do scientists track mosquito populations, and why do mosquitoes seem so much worse in summer?
Scientists track mosquitoes by monitoring where they breed and trapping adults. Field teams inspect standing water from ponds and wetlands to flowerpots, gutters and other containers for mosquito larvae. They collect and identify the larvae, which helps reveal both mosquito numbers and the species present.
Researchers also use specialized traps to catch adult mosquitoes. Some rely on light, while others mimic the signals of a human or attract females looking for places to lay eggs. These traps help scientists follow mosquito populations over time, map where different species are active, and test mosquitoes for disease-causing pathogens.
Summer provides mosquitoes with ideal conditions. Warmer temperatures speed mosquito metabolism and development and shorten their life cycle, so multiple generations can emerge in a single season. Higher temperatures also increase mosquito reproduction and enable females to produce eggs more frequently.
In other words, summer doesn’t just make mosquitoes more noticeable — it can help their populations grow quickly.
James Shah, associate professor of Psychology and Neuroscience
Shah studies how motivation and thinking work together to shape the goals people set and how they pursue them. His research shows that goals are not just desires but mental structures that guide attention, emotions and behavior. He also examines how basic needs — like achievement, security and certainty — influence how we relate to other people and navigate the social world.
Can environmental shifts during summer — such as longer days, vacations, or changes in routine — influence goal setting and how motivated people feel to pursue these goals?
Summer often begins with optimism and ambitious plans, yet for many students and faculty, it ends with regret and a sense of missed opportunity. When the familiar routines of the academic year disappear, so does much of the structure that supports motivation. During the semester, goals are anchored to the rhythms and demands of the academic calendar: Classes, deadlines and campus life help determine when to focus and when to set work aside. Summer removes those external cues, leaving us responsible for creating our own structure.
Psychologists call this self-regulation, and it can be especially difficult without outside guidance. When there is no immediate pressure to act, good intentions can easily drift, and “I’ll start tomorrow” becomes summer’s refrain. Vague goals such as “get ahead” or “finally read more” rarely provide enough direction to inspire action. Without a clear deadline, a specific plan or a defined first step, even worthwhile goals may never get off the ground.
The solution, ultimately, is not to summon more motivation but to design better conditions for action. Replace lost routines with small, consistent habits. Set specific deadlines and share them with someone who can hold you accountable. Schedule rest and relaxation rather than simply waiting for them to happen. Summer offers valuable space to pursue what the semester leaves little room for — but to make that freedom both productive and enjoyable, give it some shape.
