Your Body Almanac

District of Columbia

Urban heat, summer ozone and ticks even inside the city.

The District's risks are mostly urban. Pavement and buildings hold heat, hot days bring ozone, and the District is still classed as a high-incidence Lyme area. Winter sun is weak for a few months.

01

Urban heat island

Roads, roofs and buildings soak up heat by day and release it at night, so city neighborhoods can stay much hotter than nearby suburbs. Combined with DC's humidity, that makes summer heat harder on your body, especially without air conditioning.

SourcesHeat Islands (US EPA)Heat Index (National Weather Service)
Stay safe in the heatAs neededOn hot days, drink water often, take breaks in the shade and plan hard work for the cooler parts of the day. Rehydrate when you sweatAs neededDrink regularly during hot work or long workouts, and add electrolytes when you sweat for more than two hours. Drink water through the dayDailyKeep a water bottle within reach and sip through the day instead of waiting until you are thirsty.
02

Ozone on hot days

Ground-level ozone forms when traffic and other pollution cook in summer sun. It irritates your airways, can cause coughing and chest tightness, and worsens asthma. It peaks on hot afternoons.

SourcesHealth Effects of Ozone Pollution (US EPA)AQI Basics (AirNow)
Check the air qualityAs neededLook up your local Air Quality Index before outdoor work or exercise, and scale back when it is high.
03

Ticks in parks and green space

CDC classes the District as a high-incidence Lyme jurisdiction, with about 11 cases per 100,000 people in 2022. Wooded parks and overgrown edges can hold ticks, even in the city.

SourcesSurveillance for Lyme Disease After Implementation of a Revised Case Definition — United States, 2022 (CDC MMWR)
Check for ticksAs neededAfter time in grass or woods, check your whole body, shower within two hours and dry your clothes on high heat. Use insect repellentAs neededUse an EPA-registered repellent on exposed skin when mosquitoes or ticks are around.
04

Weak winter sun

At about 39 degrees north, DC gets little vitamin D-making sunlight in the depths of winter, and office life keeps many people indoors in daylight hours anyway.

SourcesInfluence of season and latitude on the cutaneous synthesis of vitamin D3 (Webb, Kline and Holick, 1988)Vitamin D — Health Professional Fact Sheet (NIH Office of Dietary Supplements)
Get vitamin D from foodDailyEat fatty fish, fortified milk and UV-exposed mushrooms so you are not relying on the sun alone. Spend time outdoorsDailyGet 20 to 30 minutes in a park, yard or green space most days, walking or just sitting.