Millions of Americans remain under a dangerous heat wave as the US heads into the long Fourth of July weekend. The National Weather Service expects heat indices in the triple digits across much of the eastern half of the country. On Saturday, most of the country will be under a heat risk. The Upper Midwest and western areas of the US will be under a minor heat risk, while areas south and east will see moderate, major and extreme risk.
Thursday and Friday are expected to be the peak days of the heat, AccuWeather meteorologist Alexander DaSilva told CNET, but the heat will still be dangerous through the Fourth of July weekend. Many areas will be 10 to 15 degrees higher than the historical average in the coming days.
“Temperatures will start to fall on Sunday as the heat dome collapses and the high pressure weakens,” DaSilva said. “The heat will then move west toward the middle of the month.”
DaSilva said this heat wave is being driven by high pressure across the East Coast. Meanwhile, above-average sea-surface temperatures in the Gulf and Southeast coasts are driving excessively high humidity.
While temperatures soar to near or above 100 degrees, that’s only one factor that determines how dangerous the weather could be. Measures like NOAA’s HeatRiskfactor in other measures like humidity and the variation from usual temperatures.
“We are forecasting widespread Major to Extreme Heat Risk, meaning the heat is rare and of long-duration, affecting anyone without cooling/hydration as well as health systems, industries, and infrastructure,” said Michael Muccilli, acting warning coordination meteorologist for the NOAA and NWS Weather Prediction Center.
If you have underlying health conditions, the heat can worsen them if you aren’t careful. This may mean changing your plans or taking extra precautions if you have no choice but to be outside. In extreme heat situations, it can be a matter of life and death.
“Heat is referred to as a ‘silent killer’ because it does not have the sudden, dramatic visual impacts of other extreme weather events,” said Jessica Lee, services coordinator at the Weather Prediction Center.
Temperatures in London reached 36.4 degrees Celsius, or more than 97 degrees Fahrenheit, as Europe dealt with a deadly heat wave in June. High temperatures are expected for the eastern and central US this week.
Keep an eye on the heat
As temperatures hit over 100 degrees in some areas, be alert to weather advisories.
The Centers for Disease Control and Prevention has a HeatRisk tracking tool that gives you the daily risk level based on your ZIP code, plus tips to help manage your health in the heat. Pay attention to your weather app for temperatures and weather alerts. You may also see a feels-like temperature, which can be higher than the thermometer temperature because of humidity and other factors.
“Because the Heat Index is calculated for shady areas, it does not fully account for the potential heat stress in direct sunlight and can underestimate the heat’s effect on your body by up to 15 degrees Fahrenheit,” Lee said.
During heat waves, you may expect temperatures to cool at night, but sometimes they don’t drop enough to offer genuine relief. Cooler night temperatures give your body a chance to reset from the heat. But when temperatures remain high, your body doesn’t have that chance, which can be dangerous for your health. So even when the sun goes down, continue to pay attention to how hot it is — and not just outside your home. That means there will be no relief even at hours when the sun isn’t at its strongest.
“Unlike a tornado or a hurricane, a heat wave does not leave behind a visible path of destruction,” Lee said. “This leads to heat often being seen as a mere nuisance and not as a deadly threat, leading to a lack of urgency in response.”
If you have underlying health conditions, the heat can worsen them if you aren’t careful. This may mean staying in and changing your plans or taking extra precautions if you have no choice but to be outside.
Make sure your home is cool
Keeping your home cool during a heat wave is essential to protecting your health and that of your loved ones andyour pets.
“Stay in the coolest area of your home as much as possible,” said CNET Editor Corin Cesaric-Epple. Staying inside can also protect you against sunburns, which, aside from being painful, make it harder for you to stay cool.
In your home, air conditioning is the best way to ensure you stay comfortable and safe.
Cesaric-Epple and CNET’s Labs team have reviewed more than a dozen portable and window AC unitsand found that, of the two types of non-central air conditioning, window units have optimal cooling performance. Energy Star models can also keep you cool while using less electricity.
If you’re not in the market for a new AC unit, there are othertips to keep your home cool. Consider keeping your curtains closed to prevent sunlight from warming your home. And use weatherstripping or other materials to seal any gaps around your doors and windows to keep cool air in and hot, humid air out.
Stay hydrated
It’s especially important to stay hydrated during heat waves. Dehydration can be dangerous because your body needs sweat to stay cool. Drink water regularly and take water with you when you go outside. The CDC recommends(PDF) drinking eight ounces of water every 15 to 20 minutes when working outside in the heat. You should drink in short intervals instead of consuming a large amount all at once. And don’t overdo it: The CDC doesn’t recommend drinking more than 48 ounces of water per hour.
CNET has more advice to help you stay cool this weekend, and throughout the summer, including ahandheld fanwe recommend to help you stay cool, andheat illness signsto watch out for.