The big storm heading this way has already blown out plans for Independence Day celebrations in Kennesaw, East Point, Sugar Hill and Lilburn.

Some cities are cancelling events, some are postponing them, and a lot are praying that the weather doesn’t hit with a force that snuffs out eagerly anticipated holiday festivities.

Independence Day celebrations throughout metro Atlanta are the culmination of months of planning. Thousands of people descend on town squares, some watching from spots they’ve claimed as theirs for years. Such time-honored traditions define a community and give people a feeling of small-town togetherness.

In Marietta, Nancy Morrison has been attending the Freedom Parade with her mother for nearly half a century. “If it’s just rain, I would go,” she said. On the other hand, she said, “drenching rain? I don’t know.”

Much as she would hate to miss out on the yearly spectacle, she said, “I don’t want anybody to be in danger. People’s lives are more important.”

Today, all eyes will be on the sky — and the weather reports — as thousands of people await news on the fate of festivities ranging from the AJC Peachtree Road race to Marietta’s parade and fireworks.

“We have to take into account public safety, and we have an event where there is a significant probability of lightning,” said Kennesaw city spokeswoman Pam Davis. She said the pre-holiday concert and fireworks planned for today will be held at a later date.

Many events, including the AJC Peachtree Road race, are moving ahead with plans, hoping for the best.

“Right now we are looking to have a great event that might just be a little wet,” said Atlanta Police Chief George Turner. Rain alone will not lead to the cancellation of one of the city’s signature events, he said.

But with flash flood warnings in effect through Friday and lightning a possibility, Atlanta officials haven’t ruled out postponing the event, Turner said. It would be the first time the race was rescheduled due to weather.

In Marietta, it was a big deal Tuesday when forecasters revised the chance of rain on Thursday evening from 80 percent to 70.

If the storm hits hard enough, the Marietta parade would be cancelled until next year, said the city’s parks and recreation director, Rich Buss, though the fireworks could probably be rescheduled.

“Lightning would be our big concern,” he said. “It just puts everybody in harm’s way.”

More than 100 groups have signed up for the Marietta parade, and Buss cannot remember a year it’s been cancelled in some 20 years. He knows people want to see the Boy Scouts carry the big flag, and the Lion’s Club hand out thousands of little flags. Marietta has its off-beat favorites, as well, such as the librarians who wheel their book carts in formation and the Backyard Brigade doing their synchronized moves with folding lawn chairs.

According to the National Weather Service, “very heavy rainfall” is expected today through Friday. Strong to severe storms are possible, mainly in the afternoon and evening hours, with a flash flood watch in effect.

“It’s going to be a wet Fourth of July,” said WSB TV meteorologist Karen Minton. “On Thursday … we’re looking at rain in the morning that could be heavy. Also in the afternoon … looks like even during fireworks time.”

In Alpharetta, officials said they are moving forward with the fireworks and festivities in Wills Park.

“Moving forward as scheduled,” said parks employee Jenny Simpson. “It will not be postponed.”

Sugar Hill, however, has rescheduled its Sparks in the Park show for Aug. 3.

The show typically draws 10,000 people to EE Robinson Park, so the city faced the possibility of a large crowd without adequate shelter or a small wet crowd for a rather costly show.

The festivities and fireworks in East Point are facing just a two-day delay, with the Hometown Celebration moving to Saturday.

Officials in several cities said they would meet today to decide whether to cancel or reschedule events.

Look to ajc.com for up-to-the minute weather conditions and forecasts, as well as updates on the status of local events. City officials said city websites will also provide information on local events as decisions are made.