As of 2:12 Friday morning, Anchorage will not see real "darkness" for 28 days. Friday starts the period during which Anchorage sees the most daylight of the year.

"We like to say Alaska is the land of the midnight sun and if you're far enough north, it really is the land of the midnight sun," says Brian Brettschneider, a climatologist with the University of Alaska Fairbanks International Arctic Research Center. "We enter the 28-day window surrounding the summer solstice where even here in Anchorage we have 24 hours of daylight and/or civil twilight."

Civil twilight is when the sun drops below the horizon--so Anchorage will still have a sunset--but the sun is within six degrees of the horizon.

"So it (the sun) will be a little bit below but it's still enough light so if it was, for example, clear out you have enough light to do outdoor activities," says Brettschneider.

Because of the way light reflects and refracts in the atmosphere, some of the sun's energy gets redirected, so Anchorage won't drop totally into darkness.

Anchorage is right at the southern limit of being able to stay in civil twilight. "If you travel a little farther south, say to Kenai, they don't have any days where they have 24 hours of sunlight and twilight so Anchorage is just at the southern extent," Brettschneider says. "Then as you go farther north to Fairbanks they have 73 days and all the way up north to Utqiagvik, they have 119 days."

And when your friends and family come up to visit this summer and say they'd love to see the aurora, explain that, "No, not until the sun dips to nine degrees below the horizon." Until then, it's too light. "A good point of reference is if the sun is about nine degrees below the horizon, that's the limit where you can start to see, for example, if there's a strong aurora," says Brettschneider.

That nine-degree threshold arrives in late July or early August, so don't bother aurora hunting until then.