Climate change driving up Savannah's summer temperatures - Savannah Morning News

Climate change driving up Savannah's summer temperatures

Swelter weather: Extreme heat, warm nights making Savannah summers steamier
John Deem

Coastal Georgia is getting warmer.

While that trend is consistent across all four seasons, Savannah’s increasing instances of oppressive summer heat offer the most-obvious evidence of climate change for most residents and visitors.

Extremes get our attention, and the area is experiencing more of them.

Savannah’s annual average of warmer-than-normal summer days – based on historical data – has climbed by the equivalent of more than three weeks over the past half-century, according to an analysis by weather-data organization Climate Central.

Looking at the trend another way, Savannah averaged 29 above-normal summer days per year in the 1970s, according to statistics from the National Centers for Environmental Information. Over the past decade, the city has averaged 57 such days.

In 2023, it happened 58 times. The peak was 82 days in 2016.

The lowest totals were 11 in 1974 and 15 two years later.

Moisture matters

Through May, Savannah was 3 degrees warmer than normal, according to data from the National Centers for Environmental Information.

June has offered a warm start to this summer season. Average temperatures were already about 2 degrees above normal before this week's heatwave took hold.

Experts predict that trend will continue along the Georgia coast and across the state as pollution from the burning of fossil fuels continues to trap heat in the atmosphere.

Overall, summers in Savannah are about 2 degrees warmer than they were a half-century ago.

That may not sound like a significant change, but factors driving the trend, including more exposure to extreme heat, can have an outsized impact on everyday life.

With every degree the temperature climbs, so does the risk of potentially deadly heat-related illness.

Children, adults older than 65, pregnant women and people living with illness are particularly susceptible.

Outdoor workers and athletes are also at elevated risk – as are thousands of summer visitors walking historic Savannah’s streets, squares and riverfront.

And as those summer tourists soon discover, coastal Georgia’s persistent humidity can make uncomfortable conditions downright unbearable.

"In general, the highest humidity tends to focus within the first 5-15 miles of the coast, especially when we have south-southwest winds, said Ron Morales, warning coordination meteorologist with the National Weather Services Charleston office.

Atlantic breezes coming more directly inland, meanwhile, bring cooler air..

But when the wind does move from the south and southeast, it picks up moisture as it passes over marshlands, making the air more humid, Morales explained. That was the case Monday, as breezes blowing parallel to the Georgia coast drove up humidity levels on an already hotter-than-normal day, sending heat-index readings to near 110 degrees in some areas.

The pattern illustrates how moisture magnifies the impact of even small temperature increases, especially in areas like Savannah.

For example, an air temperature of 94 degrees with 40% humidity results in a heat-index reading of 97. Bump the humidity up just 10% with the same temperature and the heat index is 103. Go up another 10% and the index climbs to 110.

Charting heat and humidity together more effectively gauges the potential risks of being outdoors.

Humans cool themselves by using excess heat to convert beads of sweat into vapor. But as moisture in the air increases, it slows down evaporation of sweat, so the cooling effect is minimized.

That’s why just a few degrees can make a big difference in the body’s ability to protect itself from extreme heat.

Ins and outs

Hotter conditions outside also increase energy demand for cooling inside.

Georgia Power established its all-time peak generation load of nearly 18,000 megawatts on Aug. 9, 2007. Savannah (99 degrees) and Atlanta (103 degrees) set all-time records for that date that still stand.

Every degree of summer warming can increase electric bills by 3% to 4%, the company says.

With summer temperatures expected to continue to rise and an unprecedented manufacturing boom under way, Georgia’s grid faces enormous capacity challenges.

The potential temperature extremes – and growing unpredictability – related to climate change add still more complexity for utilities.

“We incorporate seasonal planning to address both summer and winter conditions into our ongoing, detailed analysis of the state’s energy needs, including peak load and energy forecasts, to best serve our customers and appropriately plan for generation needs during periods of increased demand,” said Georgia Power spokesman John Kraft. “Additionally, long-term planning and investment in our transmission and distribution systems plays an important role in reliability during such events.”

In the heat of the night

Savannah is warming more between sunset and sunrise than it is in the light of day.

Rising temperatures after dark aren’t as dramatic as sizzling summer days, but trend is still significant.

“When nights don’t cool off enough relative to peak daytime temperatures, people have a harder time cooling off,” Climate Central explained in its recent report on summer warming.

That can make it difficult for someone to recover from exposure to extreme conditions.

“Sweltering nights can prolong heat stress and related health risks during the hottest time of year,” Climate Central added. “Heat is the deadliest weather-related hazard in the U.S., and warming nights worsen heat-related health risks.”

They also can affect our ability to rest, according to research published this month in the journal Sleep Medicine Review.

“Rising ambient temperatures induced by climate change pose a serious threat to human sleep and therefore human health, performance, and wellbeing,” the researchers concluded. “In hot sleeping environments, heat production can exceed heat loss beyond tolerable levels, increasing core body temperature and disturbing the natural sleep-wake cycle with increased wakefulness.”

Steamy conditions after sunset also add stress on an electric grid already trying to keep pace with daytime demand.

“When summer nights stay warmer, air-conditioning units tend to run longer, meaning customers use more energy, making energy efficiency more important,” Georgia Power’s Kraft said. “It also further indicates the need for a diverse mix of energy sources so that we can continue to provide power around the clock, for instance after solar resources stop producing and after battery storage systems have discharged.”

Uninterrupted availability and a projected surge in demand are driving Georgia Power’s plans to make natural gas a bigger contributor to that mix, a move blasted by critics who point out that 60% of the company’s energy generation is still from fossil fuels.

Keeping it cool

With Savannah already feeling the heat, Kraft offered these tips to keep summer utility bills from soaring along with the temperature:

- Close blinds or shades to keep out the afternoon sun.
- Set the thermostat to 78 degrees or higher, or use programmable thermostats.
- Run fans to help feel cooler at a higher thermostat setting.
- Add insulation to the attic and weather stripping around doors and windows.
- Ensure heat pumps or air conditioners are working efficiently by changing the filter, making sure vents and return-air registers are clear and having the unit serviced by a reputable technician.

Protect yourself

The best way to beat the climbing summer heat is to avoid it by staying in an air-conditioned space. But that’s not always possible.

The Georgia Emergency Management and Homeland Security Agency offers these hot-weather safety tips:

- Limit exposure to the sun.
- Drink plenty of fluids and replace salts and minerals in your body.
- Limit intake of alcoholic beverages.
- Closely monitor local news outlets NOAA Weather Radio for the latest information.
- Dress in loose-fitting, lightweight, and light-colored clothes that cover as much skin as possible. Protect your face and head by wearing a wide-brimmed hat.
- Stay on the lowest floor, out of the sunshine if air conditioning is not available.
- Check on family, friends and neighbors who do not have air conditioning and who spend much of their time alone.
- Never leave children or pets alone in closed vehicles.
- Avoid strenuous work during the warmest part of the day.

Hottest of the hot

Here are the highest temperatures on record for Savannah, according to the National Weather Service:

105 July 20, 1986 July 12, 1879

104 July 20, 2000 July 19, 1986

103 July 29, 1993 July 9, 1986

102 June 23, 2022 May 26, 2019

101 July 3, 2019 May 28, 2019

Editor's note: This is part of an occasional series of stories about the impact of rising summer temperatures tied to climate change in coastal Georgia.

John Deem covers climate change and the environment in the Savannah region. He can be reached at 912-652-0213.