ST. CLOUD, Minn. — Some maple syrup producers in central Minnesota are worried that last weekend's warmup could affect production.

Temperatures were near 70 degrees over the weekend. The weather is similar to the 2012 syrup production season, which saw one of the lowest yields on record.

St. John's University biology professor Steve Saupe told the St. Cloud Times ( ) that 50-degree highs and 20-degree lows are ideal for syrup operations. Such conditions cause suction in trees that helps replace fluids lost in the daytime.

Saupe, who's also a board member at the Minnesota Maple Syrup Producers Association, said warmer temperatures during the sap run's peak mean more mold and bacteria growth. And once buds appear on trees, the sap takes on an off-taste.

The sap run typically begins in earnest around March 20, Saupe said. Workers at St. John's Abbey Arboretrum have collected about 700 gallons of sap so far. The operation has about 1,300 taps.

"Historically, I'm not worried because we're still early in the season," Saupe said.

The National Weather Service forecasts highs in the 40s or 50s and lows in the 20s in central Minnesota over the next few days.

"We went from March weather to June weather in 2012 and it never did come back," said Stu Peterson, president of the syrup producers association, who has been hearing from producers worried that this year could be a repeat of 2012. "At least this week it may come back."