Climate Criteria for Collecting Maple Sap

Maybe you’ve heard this before: in order for the sap to flow in a maple tree and harvest it for making syrup, temperatures need to be above freezing during the day and below freezing at night.  Well, we’ve been tapping maples to make syrup for several years, and I must say: assuming sap is flowing simply because it is 33°F (1°C) or above is incorrect.  There are other factors at play.