Childhood memories of trick-or-treating on chilly nights in Octobers past aren't merely nostalgia.

Decades of weather data confirm that fall weather often arrives in Georgia by Halloween. And for parts of the state this year, that will be true: The high temperature in Atlanta on Oct. 31 is expected to be 67 degrees, with temps dipping into the 40s by midnight.

But one long-term trend has scientists spooked: Atlanta's Halloweens are an average of 4.5 degrees warmer now than they were in the 1970s.

Climate Central studied Halloween temperature trends from 1970 through 2022 in 244 U.S. cities, and all but 28 showed warming October trends. This information dovetails with the National Oceanic and Atmospheric Administration's confirmation of September 2023 as Earth’s record-hottest September, with 2023's temperatures the hottest on record overall.

The above graphic depicting Atlanta's Halloween temperatures over the past 52 years shows the ups and downs that happen over time and may seem harmless. But in a fall report, Climate Central scientists said that a warming trend of several degrees causes greater risks of wildfires, seasonal allergies and shifts in ecosystems that can impact human health and the economy. 

Many factors that cause earth's rising temperatures are both human-induced and natural processes of global change, according to the U.S. Global Change Research Program (USGCRP), a national plan mandated by Congress in the Global Change Research Act of 1990 (GCRA) to coordinate “a comprehensive and integrated United States research program which will assist the Nation and the world to understand, assess, predict, and respond" to changes in climate. The USGCRP comprises 14 federal departments and agencies that conduct or use research on global change and its impacts on society.

This year, the National Weather Service predicts that Georgia has a 55% to 60% chance of experiencing warmer than average fall, with a 50% to 60% chance of above normal precipitation this season.

These changes may affect the color of leaves on Halloween day, because the timing and brilliance of fall color and leaves are also influenced by temperature, sun exposure and rainfall.

As for trick-or-treating in your neighborhood, check your local weather forecast to see if little ghosts should dress in sheets — or blankets.