Call it a seasonal trifecta: Sunday is the first day of summer, the day of the year with the most sunlight and Father's Day all rolled into one.

So let the good times roll. You're going to have plenty of time to celebrate, and at least in terms of daylight hours it's all downhill from here.

Father's Day will have more than 15 hours of sunlight, according to the Farmer's Almanac.

On the longest daylight day of the year, the sun will rise at 5:48 a.m. and set at 8:54 p.m. It won't be completely dark — at least in astronomical terms — until just after 11 p.m.

That's because of the annual phenomenon called summer solstice, said Slippery Rock University Professor Krishna Mukherjee.

Sunday also marks the start of a build up to the year's hottest months, July and August.

Contrary to popular belief that's not because the sun is creeping up on us. It's actually getting more distant.

By the 4th of July the sun will actually be five million miles further away from the Earth than it is in January, Mukherjee said. It's the sun's position in the sky that concentrates solar energy and heats up the earth over a period of about two months.

Summer will last for 93 days, ending on Sept. 23.

Pat Herold, a forecaster with the National Weather Service in Pittsburgh, said Butler County residents should prepare for “basically a normal summer overall.”

Herold said average summer temperatures in Western Pennsylvania range from the low 60s to the low 80s.

“To me it's moderate temperatures,” Herold said of what characterizes the season. “Summers aren't bad here, though humidity does get to be an issue for some people.”

As the sun gets higher in the sky, Mukherjee said, more happens on Earth than just heat: People's shadows shrink. At noon Sunday, your shadow will be the shortest of any day all year.

However, that can be tough to notice in Western Pennsylvania.

“Unfortunately, that is hard to check around here,” Mukherjee said. “We only probably get about 60 sunny days a year.”

If you're someone who enjoys a sunrise or sunset, Mukherjee said, Sunday is also special. You'll be looking at true northeast in the morning and true northwest in the evening for those events.

The only other time the sun's position is that precise, she said, is during semiannual equinoxes in March and September.

These days, Father's Day makes a bigger publicity splash than the solstice, but it wasn't always that way.

“Historically today has tremendous importance,” Mukherjee said. “Ancient astronomers in all cultures erected monuments to observe this specific day.”

For the college professor, though, it can be a slightly sad time.

“Right after the solstice, the days start to become shorter, and that's a little sad for me,” Mukherjee said. “It's kind of a mixed feeling.”

What should you do with the longest day of the year? The good news is that there's plenty to choose from — whether you want to stay close to home or get away.

If you're staying close, be prepared for company, said Jack Cohen, president of the Butler County Tourism and Conention Bureau.

Summer kicks off the county's busiest season, Cohen said, with more than 1 million visitors crossing the county line in the next few months.

One of the biggest attractions is Moraine State Park, where families and groups often hold events on Father's Day, said park manager Dustin Drew.

Drew said the park has a marked increase in visitors on Father's Day, with activities like boating, fishing and picnic outings topping the list of things to do.

“There's certainly a lot of different things you can get into here,” Drew said.

In addition to hiking and swimming, the park also offers opportunities to glimpse birds of prey like Osprey and Bald Eagles.

Drew said that yearling deer and black bears have also been active throughout the park in recent weeks, and are proving to be draws for visitors hoping to catch the animals in action.

If you would rather get out of town, though, Heather Metallo of Premier Travel in Butler said now is usually the time people pick to start slipping away for a little relaxation.

“It definitely kicks off (the season) for us,” she said of the start of summer. “There are a lot of people leaving this week.”

Metallo said vacation plans are more concerned with when the children will be out of school, so June, July and August are naturally the most popular months.

Metallo said the average summer getaway vacation lasts for seven days and six nights, and can take up to two weeks to plan.

Looking forward to summer temperatures? Here is what they were a year ago from temperature readings at the Butler County Airport.<b>June 2014</b>Average high: 78.3Average low: 58.6<b>July 2014</b>Average high: 78.3Average low: 58.9<b>August 2014</b>Average high: 78.3Average low: 57.7<b>September 2014</b>Average high: 73.3Average low: 52.2

<b>Looking for something to do on Father's Day? Here are some ideas.</b>Antiques & Artisans Festival, Whispering Pines Farm, CabotSummer Sailstice, Watts bay with Moraine Sailing ClubNautical Nature Pontoon Cruise, Lake Arthur, Moraine State Park<b>Looking for something to do this summer? Here are some ideas.</b>June 28: Cruise-A-Palooza, Butler Farm Show groundsJuly 3 to 11: Big Butler FairJuly 9 to 11: Cranberry Township Community DaysJuly 18: Celebrate the Bloom, Slippery RockJuly 20 to 25: Saxonburg CarnivalJuly 30 to Aug. 2: Portersville Steam Show,Aug. 1 to 2 Regatta at Lake Arthur, Moraine State ParkAug. 8: Pro Disc Golf World Championships, Moraine State Park.Aug. 10 to 15: Butler Farm ShowAug. 18 to 22: North Washington Rodeo