Iowa sap flow forecast

The next several days for Iowa's sugaring country, read the way a sugarmaker reads them: how cold the night gets, how warm the afternoon gets, and whether that adds up to a run. The season here usually opens mid-to-late February.

ISU says Iowa's commercial producers are in the northeast; Chickasaw, Winneshiek and Fayette counties report 29% of Iowa's taps, and Winneshiek County (Decorah) the most syrup (2022 Census of Agriculture).

Forecast for Decorah

Updated Sep 26, 6:31 AM EDT

No freeze-thaw days in the forecast

Blue = below 32°F · Amber = thaw · dashed line = freezing

  1. SunSep 27
    66°high
    55°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 55°F — trees need a hard freeze to reload. No freeze, no run.

  2. MonSep 28
    70°high
    56°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 56°F — trees need a hard freeze to reload. No freeze, no run.

  3. TueSep 29
    67°high
    55°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 55°F — trees need a hard freeze to reload. No freeze, no run.

  4. WedSep 30
    68°high
    58°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 58°F — trees need a hard freeze to reload. No freeze, no run.

  5. ThuOct 1
    67°high
    57°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 57°F — trees need a hard freeze to reload. No freeze, no run.

  6. FriOct 2
    65°high
    51°low
    0h frozen
    20h thawed
    No freeze, no run

    Low of 51°F — trees need a hard freeze to reload. No freeze, no run.

Data: National Weather Service. Verdicts use freeze-thaw thresholds from maple field research; your woods may run a little differently.

Somewhere else in Iowa?

Your sugarbush, your forecast

Hourly temperatures for your exact spot, turned into a day-by-day sap-run outlook. US and Canada.

Planning ahead? Typical tapping dates for Iowa →

Data & method

  1. National Weather Service API — NOAA National Weather Service
  2. Sap flow in sugar maple: timing and weather drivers (Frontiers in Agronomy, 2025) — de Lima Santos et al.
  3. Maple Sugaring Tips for Beginners and Backyard Maple Sugar Producers — UNH Extension
  4. North American Maple Syrup Producers Manual, 2nd ed. (Bulletin 856) — The Ohio State University Extension

Never miss the first run

LuckySap can ping you the evening before a strong sap day, then keeps your collections, sugar readings, and boils in one season log. Free on iPhone.

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