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Phenology Report: Spring melt and migration comes a month early

Lake ice melts in Chippewa National Forest on March 4, 2024.
Angela Nistler via KAXE-KBXE Season Watch Facebook group
Lake ice melts in Chippewa National Forest on March 4, 2024.

Ice-out calculations

Have I mentioned how much I adore the KAXE/KBXE community recently? Y’all are a delightful bunch, I’m glad to have found myself among you.

Here's why: During this week’s report, John mentioned a formula developed by John Downing to calculate when ice would disappear on local lakes.

To my lasting amusement, the audience reaction was not “Ew, math,” but instead, “A formula? What is it? I must make calculations immediately!” We had multiple people reach out asking for the formula.

For those with the first reaction, don't worry: you can skip the math and use John Downing's widget, which performs the calculations for regions throughout the state.

Flowering speckled alder catkins hang down from a bare branch. They are long and maroon with yellow flecks. The background shows a bare deciduous forest and blue sky.
iNaturalist user joebartok
Flowering speckled alder catkins hang down from a bare branch.

For the rest of you delightful dweebs, never fear! I have heard you, and the calculations to predict ice-out locally are below (including examples.)

Want to learn more? Check out the Minnesota Lakes Ice-Out Clock here, register for their March 8, 2024 webinar here, and/or enjoy John and Heidi’s interview with John Downing here. (I’ve added the formula to that article you won’t have to click back and forth.)

Time stamps:

  • Early spring (0:14-1:07)
  • Robins (1:07-2:45)
  • Early migrating arrivals (2:45-4:55)
  • Ruffed Grouse (4:55-5:28)
  • Trumpeter Swans (4:55-6:26)
  • Ice-out timing and predictions (6:26-7:33)
  • Birds coming to feeders (7:33-7:52)
  • Snow Buntings (7:52-8:08)
  • Bald Eagle nesting update (8:08-9:21)
  • Maple bud and sap update (9:21-11:18)
  • Budding updates (11:18-14:38)
    • Birch (11:18-11:39) 
    • Elderberry (11:39-11:54) 
    • Speckled alder (11:54-12:38) 
    • Fly honeysuckle (12:38-13:48) 
    • Juneberry (13:48-14:24) 
    • Balsam fir (14:24-14:39) 
  • Forest colors (14:39-15:56)
    • Trialing arbutus (14:39-15:21) 
    • Bunchberry (15:21-15:42) 
    • Sedges (15:42-15:56) 
  • Wooly bear caterpillar (15:56-16:48)
  • Bucks with antlers (16:48-17:17)

Do the math!

(Please note that this formula has absolutely nothing to do with ice safety: the ice is unsafe long before it disappears.)

An image shows an example forecast for early spring, with the following highs and lows: Wednesday 41/28, Thursday 33/15, Friday 31/18, Saturday 37/17, Sunday 43/27, Monday 51/34, Tuesday 49/38, Wednesday 47/31.
National Weather Service
An image shows an example forecast for early spring in Grand Rapids. The example is for March 6-13, 2024.

  1. For each day with a temperature exceeding 32 degrees Fahrenheit or 0 degrees Celsius, calculate the average temperature for the day: Add the high and low temperature together, then divide by two. (For instance, the Saturday highlighted above would have an average temp of 27 degrees. First, 37 + 17 = 54. Then, 54 / 2 = 27.) 
  2. To calculate the degrees warming, subtract 32 from that number. Skip this step if you are using degrees Celsius. (Saturday's degrees warming would be minus 5: 27 - 32 = -5).  
  3. If your result is a negative number, change it to 0. (This applies to our example Saturday: we change minus 5 to zero.) 
  4. To calculate warming degree days over the season, add each day's result to a running total. (For example, let's use the eight days in the forecast above: 2.5 + 0 + 0 + 0 + 3 + 10.5 + 11.5 + 7 = 34.5 warming degree days.) 
  5. Once the season's warming degree days reaches 220, your local lake should be clear of ice. (Please note that rivers play by entirely different rules: they will be ice-free much earlier.) 
  6. Let us know how this worked for you! 

That does it for this week! For more phenology, subscribe to our Season Watch Newsletter or visit the Season Watch Facebook page.

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

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Charlie Mitchell (she/they) joined KAXE in February of 2022. Charlie creates the Season Watch Newsletter, produces the Phenology Talkbacks show, coordinates the Phenology in the Classroom program, and writes nature-related stories for KAXE's website. Essentailly, Charlie is John Latimer's faithful sidekick and makes sure all of KAXE's nature/phenology programs find a second life online and in podcast form.<br/><br/><br/>With a background in ecology and evolutionary biology, Charlie enjoys learning a little bit about everything, whether it's plants, mushrooms, or the star-nosed mole. (Fun fact: Moles store fat in their tails, so they don't outgrow their tunnels every time conditions are good.)