A day’s highest (maximum) temperature usually occurs in the afternoon. Averaging the daily high temperatures over any period results in a mean maximum temperature for that period.
Maximum temperature serves as one measure of comfort and safety for people and for the health of plants and animals. When maximum temperature exceeds particular thresholds, people can become ill and transportation and energy infrastructure may be stressed.
A day’s lowest (minimum) temperature usually occurs in the early morning, just before sunrise. Averaging the daily low temperatures for any period results in a mean minimum temperature for that period.
Periods of low temperature give plants, animals, and people a chance to recover from daytime heat. When minimum temperatures aren’t sufficiently cool, plant and animal responses can trigger ecosystem changes and increased demand for energy can stress energy infrastructure.
The number of days per year when locations receive more than 1 inch (2.5 cm) of precipitation is an indicator of how often heavy precipitation events occur. This measurement may also be used as an indicator of flood risk.
Comparing values at a single location over time can indicate a trend of increasing or decreasing flood risk. Comparing values from one location to another may not reflect relative risks for flooding, as factors that control runoff vary from site to site.
Daily totals of rain and snow vary from zero to several inches; averaging these totals over a period gives an average daily value. Mean daily precipitation indicates the average amount of water added to the environment each day.
Mean daily precipitation is one indicator of how wet or dry a place may be at different times of the year. Comparing values for mean daily precipitation over time can indicate a trend toward wetter or drier conditions.
The number of heating degree days per year reflects the amount of energy people use to heat buildings during the cool season.
For example, many people like to keep indoor temperatures at 65°F. On a day when the average outdoor temperature is 55°F, raising the indoor temperature by 10 degrees over 1 day requires 10 degrees of heating multiplied by 1 day, or 10 heating degree days. Utility companies use heating degree days to estimate the annual amount of energy people will use to heat buildings.
The number of cooling degree days per year reflects the amount of energy people use to cool buildings during the warm season.
For example, many people like to keep indoor temperatures at 65°F. On a day when the average outdoor temperature is 85°F, reducing the indoor temperature by 20 degrees over 1 day requires 20 degrees of cooling multiplied by 1 day, or 20 cooling degree days. Utility companies use cooling degree days to estimate the annual amount of energy people will use to cool buildings.
The total number of days per year with minimum temperature below 32°F (0°C) is an indicator of how often cold days occur.
Below-freezing temperatures can cause driving hazards, aircraft icing, and damage to infrastructure. However, ski resorts and other winter recreation businesses depend on days with below-freezing temperatures to maintain snowpack. Additionally, some plants require a period of days below freezing before they can begin budding or blooming.
The total number of days per year with maximum temperature above 95°F (35°C) is an indicator of how often very hot conditions occur. Depending upon humidity, wind, access to air-conditioning, humans may feel very uncomfortable or experience heat stress or illness on very hot days.
Hot days also stress plants and animals as well as infrastructure. Increased demand for cooling can stress energy infrastructure.
We evaluate climate over long periods of observation. For example, in 2014, the global temperature was 1.24°F (0.69°C) above the long-term average for the 20th century, according to NOAA's National Climatic Data Center. That number made 2014 the warmest year on record in the NOAA database, which goes back to 1880.
Data source: NOAA, 2015 3
Data source: NOAA, 2016
As sea level rises, so do instances of flooding along the coast. Rising waters increasingly threaten buildings and infrastructure through storm surge, strong waves, heavy precipitation, and high-tide "nuisance" flooding. Property owners and municipalities can check their vulnerability to coastal flooding from current flood hazards as well as future sea level rise.
Data source: NOAA, 2015
Ecosystems that serve as natural sources of food, timber, and clean water are increasingly threatened by changing conditions. View landcover, wetlands, and rivers & streams to visualize the location and extent of land-based ecosystems. Compare these locations to climate stressors such as sea level rise and drought.
Climate change increasingly impacts land, foods, and lifestyles of American Indians. Survey the extent of Indian land and explore landcover and social vulnerability in these locations. Check the land's vulnerability to climate stressors such as sea level rise, flood hazards, and drought.
Changing conditions are increasing threats of both flooding and drought. Flood zone maps can help you identify areas that are at risk of flooding and the current drought layer shows which regions are abnormally dry or experiencing drought. View the land cover layer to get a sense of what may be impacted by flooding or drought.
Extreme events increasingly threaten land-, water-, and air-based transportation systems and supply chains. View the location of transportation assets such as highways, bridges, and airports, and check to see where they coincide with flooding hazards and the risk of inundation from sea level rise.
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