Welcome to summer, Philadelphia.

Thursday marks the 2018 summer solstice, or the longest day of the year for those living in the northern hemisphere. It's also recognized as the first day of the astronomical summer.

Philly will see 15 hours of sunlight throughout the day, nearly six hours more than the region saw during the winter solstice in December. That means there's plenty of time to fire up the BBQ, head out to the pool or just hang out in the hammock in the backyard.

Here's a few things you should know about the event.

What is the summer solstice?

Aside from being the longest day of the year and marking the start of the season for sunburns and cookouts, the summer solstice happens when the sun is directly over the Tropic of Cancer, according to the National Weather Service. For our region, the solstice occurred at 6:07 a.m.

This year's winter solstice, the shortest day of the year, which happens when the sun is over the Tropic of Capricorn, will be on Dec. 21 at 5:23 p.m.

What’s the weather going to be like?

While the day will be long, it's not clear how much sunshine the region will be seeing. There is a chance of showers during the afternoon, according to the weather service. Tonight will be partly cloudy with a low of 65 degrees. Storms and showers are likely over the weekend.

What’s going on Philly?

There are a handful of celebrations happening around the Philadelphia area, including a music and food festival in Haddon Township and moon rowboating event at Bartram's Garden in Southwest Philadelphia. There's also a yoga class happening on the Race Street Pier in celebration of the summer solstice.

Not looking for an organized event? There's plenty of options for you, too. Philadelphia's public pools open this week, and there are multiple natural swimming spots within an hour's drive of the city. Restaurant columnist Michael Klein also has a quick roundup of beer gardens and where to get the best outdoor seating.

Why are people talking about Stonehenge?

The cosmic event is believed to have been celebrated for thousands of years at the prehistoric landmark found in the United Kingdom, according to TIME. This year, roughly 9,500 people flocked to Stonehenge to watch the sunrise at 4:52 a.m.