It's a sweet sign of spring.

The sap is running, and the Wargo Nature Center in Lino Lakes is ready to tap into it during Sunday's Maple Syrup Madness festival.

"It started 13 years ago, actually as a maple full moon event," said Deb Gallop, program supervisor at Wargo. "In 2004 we switched it to a day festival, and it's been a wonderful family event."

The event attracts an average of 100 participants, and it happens rain or shine.

But the conditions have to be perfect for maple syrup making.

"It has to be above 40 [degrees] during the day, and under 30 at night," said Jennifer Fink, marketing and visitor services manager at Anoka County Parks and Recreation. "That's what causes the sap to run. Some years are better than others, but it's always fun to teach folks about it."

All stages of the maple syrup process will be shown and demonstrated by the Nature Center's naturalists. The history of maple syrup making will be covered, dating to the 19th century.

The actual process itself hasn't changed much over the years. In the spirit of the old tradition, the sap will be collected from the maple trees, then cooked down over an open fire. But there also is an evaporator for use on-site, so participants can take in the modern-day maple syrup processes as well.

The Nature Center event incorporates many other activities along with the maple syrup making. Visitors can participate in a hike where they see tapped trees, learn about the process of making sap into syrup, as well as craft making.

"It's a lot of families, from parents with young kids all the way up to empty nesters," said Fink. "It really varies, and it's a free-flowing event where people get to choose what they want to listen to, what interests them."

Everyone's favorite, especially the kids', seems to be the taste-testing, Fink said.

All sorts of maple syrup treats are available, from maple syrup baked beans to log cabin sundaes, which are topped with maple syrup made at the center.

The syrup tasting is an education in itself, Fink said, with many people not believing the difference when they taste the product for the first time.

Fink and Gallop said it's a treat to see the kids stick a finger under the spout and taste the sap.

"What they think is maple syrup from the store, and what true maple syrup is that gets made right in front of their eyes. ... There's definitely different grades of maple syrup," said Fink. "Most of the stuff in the store is flavored with additives, to make it taste like maple. The actual stuff you'll taste at our event is lighter in color, and it's a much softer taste. ... It's just more subtle."

Kelly Jo McDonnell is a Twin Cities freelance writer.