A Little Science behind Maple Sugaring Weather

Hands down, the number one question that comes up this time of year is “When should I tap?”

Due to the warmest December on record, I have heard a few Ohioans even asking “Should I have tapped in December?”.  When you look back over the years, the trend has been toward earlier tapping dates, but hoping that you can keep taps open for 3+ months is a bit of a stretch.  There is no way that will happen on a gravity system, and you will need more than a little luck even on high vacuum.

The scientific approach to planning involves studying climatological data and developing a plan based on that data. The maps below are long range weather predictions for the next three months. You can clearly see that all indications point to above normal temperatures for the next three months. For sugar makers what does this mean?

To quote a good friend and fellow maple researcher, “when you look at forecasts you need to look at it from the big producer / small producer perspective.”  Because most small producers tap everything at one time, they need to consider the value of a good short-term, 30-day forecast.  In most cases, especially if you are on a gravity system, you need to find the best 30-day window that will allow you to make the most syrup.  Once you tap, you are on the clock and that clock runs out shortly after 30 days.  On the other hand, if you are a large producer or even a medium producer on vacuum, you need to study yearly trends.  Trends will disclose what has happened over the last 3 to 5 years.  What we have seen is a trend to earlier tapping just about every year.  In most cases, early tapping has paid off in Ohio.  A major reason is that newer technology lends itself to pushing the envelope when it comes to tapping.  You have the advantage of running a semi-closed vacuum system utilizing 24/7 operation.  This lengthens your season considerably.

One of the most valuable pieces of data you can use are temperature history graphs for your location.  Weather Underground has some of the best.  They plot the maximum, minimum, and average temperatures.  Plotting the maximum and minimum will give you a good idea on the number of freeze-thaw days to anticipate for a month.  As we all know, freeze-thaw cycles are very important and drive daily sap runs.  You can look at these cycles over a five or even ten year period.  Over time you begin to see how various weather patterns play out.

Keeping in mind these are zip code specific but we are talking at the broad scale of an entire state, here are three February graphs. You can clearly see we started February leaving a warm end to January on two out of the three graphs.  In all the graphs, conditions continued to warm up as February wore on.  In two out of the three, the temps dropped going into March.  This may be a hint for what could happen this year.  2020 and 2022 were almost normal.  In both cases, our records show average to above average production.  2021 was the outlier and production was down for that year as temperatures stayed warm through most of March.  The other two years highlight the fact that starting out February warm does not mean you will march into March warm.

Too much science?  Here is a more common sense approach that prioritizes the size of your operation.  If you are tapping thousands of taps, you must start early to get the job done.  For a moment, think about a huge 50,000-tap operation.  Should they consider tapping right after the first of the year?  Definitely!  One of their strategies is to tap 5,000 taps super early.  This results in the Facebook posts you may have seen bragging about syrup being made over Christmas.  Several big producers in the East did this in December.  Does that mean they tapped everything?  Most likely not.  A large commercial producer hedges their season by tapping some early and the rest over the month of January with everything in the tree and ready by February 1.  Small producers who are setup to boil early can also do this, the only difference is they may start tapping their early running trees shortly after New Year’s but plan to finish out in February.  This keeps fresh taps in the system and prevents you from putting all your eggs in one basket.  The best way to accomplish this is to keep very good records.

That brings us back to our initial question.  When should I tap this year?  All indications are that we are going to have a warmer than normal winter.  If you are in Southern Ohio, you might be tapped already.  North of I-70, you should probably hold back until the end of January.  This is where analyzing the 30-day forecast is critical.  Studying several long-range forecasts a little closer, I noticed that we may have some of the coldest weather of the winter on the last week of January and the first week of February.  While the forecast is showing a warming trend coming off several weeks of genuine cold weather, depending on your situation you may even want to hold off until the first week of February.

Of course, the joker in the deck is the El Nino weather event we are experiencing.  El Nino’s are known for extremes and all it takes is a bend in the jet stream and you could be looking at 10 more days of below average weather.  Once this happens, you usually go right back to the warmer than normal pattern.  In this case, cold weather is your friend.  What we do not want is 10 days straight above normal!

As for my prediction!  I will tell you what kind of season we had in 2024 on the first week in April.  May your sugar season be long and sweet.

14 thoughts on “A Little Science behind Maple Sugaring Weather

  1. Thanks, Les. Good, thought-provoking piece. As a small producer on buckets I’ve often wondered about hedging my bets by placing only a portion of my taps when I would normally place all of them at once. Maybe place half, then two weeks later place the remainder. You will miss out on some production but you will also be guaranteed to catch the earliest and latest runs of the season. Over the years would I come out ahead?

    • Marc

      You can do that but as a small producer when it comes to tapping time with buckets you need to find the sweet spot on the calendar. No pun intended. Look for a time in the upcoming 30 day forecast when you have freeze thaw weather in your area. That is low twenties at night and mid forties during the day. That could be February or March depending on where you live. you need to find a 30 day window because that is about all of time you have once you tap with buckets.

  2. If you look at the weather forecast for Billingstown, OH, we have a freeze thaw cycle coming up this weekend for a few days and then the temperature is predicted to stay above freezing with highs in the upper 40’s and 50’s the first week of Feb. We do 120 taps and try to get the best 30 day window.

    Do you recommend we tap this weekend for the best quality and volume? If not, when would you suggest?

    We are not sure if it is best to tap the first time the temperature looks to be consistently above freezing, or wait until it looks like there would be more freeze thaw cycles later (which might never come). We tapped first week of March in 2022 and Feb 5 in 2023.

    Our thinking has been the first window that looks to stay above freezing, but are not sure if we are jumping the gun too soon.

    Thank you very much for your help

  3. Les will likely chime in, but with 120 taps I’m assuming you are using buckets or bags? When that is the case, you only have about 30 days of good sap flow before things start closing up quick.

    Also, are you working with sugar maple or red/silver maples? If sugar maples, then you have a much longer window before too many warm days push them to bud break. In other words, waiting another week or two is less likely to be a dealbreaker. If the latter, that window is a lot shorter and the early birds are more likely to get the worms.

    I will say this – the forecast for Mansfield looks just about identical to yours, but we have tubing on vacuum and a mix of maple species in our woods. We are probably going to tap Sunday-Tuesday AM to get a good flush on the system and pray for good runs Wednesday and Thursday before it warms up and stays above freezing. I say probably though because you just never know how the leading edge of the forecast will change as the calendar continues chewing up the days. Bottom line – looks like the El Nino pattern we all feared is starting to show, but thank goodness for a cold January!

    • Buckets and red maples.

      It’s staying above freezing now. Would you suggest tapping Friday this Friday when the rain stops?

      Thank you very much for your help. Look forward to what Lee has to say also.

      • Red maples…if it were me and I had the bandwidth to start boiling, I’d go for it. I’m sure he will chime in sometime soon. No matter what you decide, I hope it’s a solid season for you!

      • Buckets and Red Maples make things a little different than buckets and sugar maples especially in NW Ohio. Looks like you will get a good run on the first two weeks of February. With Sugar Maples I would be eyeballing the forecast for March. With a 30 day window I would not want to cut myself out of the good runs in early march because I tapped in January and my taps ran out. However, with Reds the season can end a lot quicker than you like. You have to factor in that early end syndrome. Pick the most promising stretch weather in February and tap. Hope you can make it into March.

        • Thank you very much for your help. We will probably tap the 28th, but look at the 2 week weather then to decide for sure.

        • To get into March, I would have to tap after the first week of Feb. If you had the flexibility to tap anytime like we do, would you recommend that we do this and not worry about the first week of Feb where the highs are in the 40’s and 50’s but not much below freezing? Being red maples, not sure if this weather pattern shortens the sap flow window, or would you think it would be still flowing well into mid March? Nothing is for sure, but sure would like to hear more of your opinion on this. Thanks again for all of your help.

          • Just checked your Billingstown, OH, forecast again. On the site I checked, there isn’t a single day forecast over 50 degrees F. So while it will stay above freezing more days than not, and the low temperatures won’t generate many of those hard resets that are needed to stimulate sap flows, the forecast is not warm enough to start churning out Growing Degree Days (GDDs). Remember that red maples start waking up at temps over 50 F, but their alarm clock won’t be ringing much in the next 2 weeks if the forecast is to be trusted. Oh to have a crystal ball for what the rest of February and the first half of March hold in store!

    • Ed
      Check values were designed to keep microbial saturated sap from entering the tree. This kept the taps from healing sustaining the sap flow at the end of the season. Unfortunately research on check valves lengthening the season was inconclusive. I personally used check valves for over 10 years. I saw an ability to lengthen a normal season by 7 to 10 days. When you had an extremely warm season this advantage broke down. Many producers saw the balls inside the spouts gumming up and sticking. This blocked the flow from the spout. It did not happen everywhere but it did happen. Also in high vacuum systems that keep the vacuum on 24/7 there is no advantage to using check valves. There is also not advantage to use ck valves in a gravity system. They were designed to be used in a vacuum system. You can find additional information using ck valves in the Cornell Maple Program Tubing and Vacuum Notebook and research studies from the UVM Proctor Maple Research Center. hope this helps.


  4. Hello. I have a very small operation with buckets and mostly black maples. I am in Powell, just north of Columbus. I had some decent days early, but almost nothing since. I am halfway through the 30 day window and am worried this will be a very bad year for me. I have operated with a rule of one bucket per maple per season. If late Feb to mid March looks promising, I was thinking of moving some of the buckets and re-tapping some of the larger trees (greater than 15” diameter) for a second tap this season. Also, do you think the poor runs this past week is because nights have not been cold enough to re-set the trees or could low soil moisture be contributing? We are pretty dry for this time of year. Thank you!

    • The short answer is yes. A soft reset does not do much good, say overnight lows of 30-32 degrees. If you think about it, a night that to 30 degrees isn’t usually actually that cold for very long. Down in the upper 20s or colder is necessary for a good quality hard reset. Additionally on days that aren’t too much above freezing (say 36-38 F for example), producers on buckets may not get much, but a tubing system on vacuum may have a decent run. And as for moisture, it’s pretty dry in the woods. We have had crunchy leaves for almost a week in our sugarbush before some rain rolled in earlier today. Best of luck rest of season, the only constant seems to be surprise and change!

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