What’s going on with the weather? Usually at this time of year in Wisconsin, snow covers the ground in groves of maple trees. But right now, farmer Jeremy Solin doesn’t even need a jacket! Sap drips from trees. The ground is muddy. That can mean only one thing: spring thaw.

But the timing is off. “It’s just very disorienting,” Mr. Solin says.

He isn’t the only maple syrup producer feeling this way. In many parts of Wisconsin and the Midwest this year, the warmest winter on record drove maple sugar farmers into the sugar bushes early. They collected sap for syrup a month or more earlier than normal.

Maple farmers start with lots of maple trees. They drill a hole in each tree. Then they put in a spile (a spigot for sap to flow through). Buckets below the spiles collect sap. Some farms use tubes that carry the sap to tanks.

Producers boil the sap until most of the water has evaporated. Only sweet, sticky maple syrup remains. It takes about 40 gallons of clear, slightly sweet sap to make one gallon of maple syrup.

For sap to flow, maple farmers need warm days and cold nights. Early spring can be fun at the end of a long winter. But syrup makers think, “Wait a little longer!” When trees bud, the sap flow slows.

With the arrival of spring, maple trees start to “wake up.” During cold nights, the sugar in sap works as a kind of “antifreeze.” The sap flows down. Farmers catch it as quickly as they can for boiling.

But timing is everything. Tapping the trees too soon doesn’t work. After a few weeks, each tree heals. The hole closes up.

Maple sugar farmers plan to collect sap in March and April. But this year the flow started in January. Some farmers missed that first run—and lost gallons of syrup as a result.

What syrup weather will next year bring? Farmers will watch and wait—with their buckets ready.

And out of the ground the Lord God made to spring up every tree that is pleasant to the sight and good for food. — Genesis 2:9