Summer is officially underway in the northern hemisphere beginning today, June 20th. Quite the range of weather conditions are forecast across the United States today. In the East, a cold front moves offshore New England and stalls across the Carolinas. Showers and storms remain a threat near the stalled boundary from the Carolinas to the Gulf coast, while comfortable 50 degree dewpoints filter in behind the front in the Northeast. Cloudiness and rain chances will keep high temperatures near to below average across this region for the start of summer.
Residents along the Gulf Coast are watching a tropical storm brewing over the north central Gulf of Mexico. Louisiana residents are beginning to feel the effects from the outer rainbands of the storm. Flash Flood Watches are in effect from Southeast Louisiana to the eastern Florida Panhandle. Tropical Storm Warnings are in effect for portions of the Louisiana and Texas coastlines.
Across the Great Plains, temperatures are near average with mostly sunny skies to start the season. While this afternoon will be warm, in the upper 80s to low 90s, outdoor temperatures will feel more comfortable than they did over Father’s Day weekend. If you live in Central Oklahoma, like me, you may recall dewpoint temperatures climbing to 75 degrees Saturday morning, and persisting near 73 degrees through mid-afternoon. Dewpoint temperatures are a measure of moisture in the atmosphere, so higher dewpoints correlate to higher moisture content and humidity. Although the actual high temperature was only 92 degrees, when you factor in the moisture and humidity, the maximum heat index was 104 degrees.
What does this mean? Heat Index calculations use air temperature and dew point temperature to determine an “apparent” temperature, which is how your body feels when you are experiencing summer heat. The National Weather Service (NWS) Heat Index calculations are for shady areas, so it’s important to know that direct exposure to sunlight can increase the “apparent temperatures” by 10 to 15 degrees. High heat index values, generally over 100 degrees, are given an heightened awareness of hazardous outdoor conditions. Local NWS offices issue special heat advisories and excessive heat warnings for moderate to extreme heat indexes, when the risk of heat-related illnesses is highest. A day with a high heat index feels uncomfortable and sometimes oppressive. Sweat is slow to evaporate and the body struggles to cool down. Direct exposure to the sun only exaggerates this.
But, it’s not just the feel-like temperatures that are uncomfortable and dangerous. In the desert southwest, temperatures are normally in the 100s in June with very low dewpoints. The start of the 2017 summer will be no different with above average, and potentially record-breaking heat, forecast across much of the Southwest.
Heat advisories and excessive heat warnings are in effect for Arizona and portions of California and Nevada through Friday. Hot summer days in the desert can feel like you are walking into an oven! Outdoor structures, such as playgrounds, are often unusable. A recent test in Tuscon, Arizona found that a children’s slide in the sun can reach 150 degrees, which is more than hot enough to cause a second-degree burn.
Take precautions and stay safe during the 2017 summer season!