Extreme heat events are the most dangerous natural hazard in the United States, contributing to an average of 675 deaths per year. In fact, on average, excessive heat claims more lives each year than floods, lightning, tornadoes and hurricanes combined.

According to the U.S. State of the Climate report, 2012 was the warmest year on record in the contiguous United States, in records dating to 1895. In 2012, Baltimore City had its warmest year on record since 1949.

2012-temps_Difference from normal

Average air temperatures are projected to increase by about 3°F by mid-century. Average summer temperatures could increase by as much a 9°F later in the century, leading to extended heat waves.

The Heat Index is a measure of how hot it really feels when relative humidity is factored with the actual air temperature. To find the Heat Index temperature, look at the Heat Index chart below. As an example, if the air temperature is 96°F and the relative humidity is 65%, the heat index–how hot it feels–is 121°F. The Weather Service initiates alert procedures
when the Heat Index is expected to exceed 105°-110°F (depending on local climate) for at least 2 consecutive days.

NOAA Heat Index

Heat is a major concern in Baltimore City. Typically, metropolitan areas are consistently hotter than surrounding areas because asphalt, concrete, steel and bricks absorb sunlight and release heat back into the atmosphere. This phenomena is referred to as the Urban Heat Island.

There is a significant relationship between temperature and land cover as shown in the pair of images below. The image on the left shows highly developed areas (those with a high concentration of cement and asphalt) in red, while white areas are primarily covered by plants and trees. The image on the right shows the approximate land temperature of the land surface on a summer’s day. The highest temperatures are in white and yellow, while cool temperatures are in purple.

baltimore_DevelopedLand_earthobservatory  baltimore_UHI_earthobservatory

baltimore_lcc_palette  UHI_baltimore_etm_2001214_palette

For more information on preparing for heat events in Baltimore City, please visit: http://baltimorehealth.org/info/emergency/code-red/2009_06_25CodeRedGeneralreduced.pdf

What is your biggest concern related to heat in Baltimore City?

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