Climate Fact: North American Extremes
The concepts of weather extremes and thresholds are tightly coupled and important to remember when planning effective and reliable infrastructure. For example, just one day of extreme heat, even if it falls during a particularly cool summer, can cause railroad tracks to buckle and transportation systems to shut down. Extreme rainfall can have similar effects; highways are designed to function during moderate rainfall events, but underpasses may flood during extreme events. Two inches of rain in a 24-hour period is considered to be a threshold that, when exceeded, forces the average municipal water treatment facility to discharge untreated sewage into local surface waters, where it may poison wildlife and ultimately be hazardous to people in the municipality it serves. Over the past 40 years in North America (including Hawaii, Puerto Rico and the U.S. Virgin Islands), the average highest summertime maximum and minimum temperatures at weather stations have increased by 1.6 degrees Fahrenheit, while the lowest winter maximum and minimum temperatures have increased by 6.3 degrees Fahrenheit. The average amount of precipitation falling during the highest one-day and five-day precipitation event periods has also increased.
Seasons: Winter, Spring, Summer, Fall
Source: Peterson, TC et al. “Changes in North American extremes derived from daily weather data.” Journal of Geophysical Research: Atmospheres 113 (2008): D07113.
