Illinois sap flow forecast

The next several days for Illinois'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 early January (south) to mid-February (central).

Central Illinois reference point: Funks Grove in McLean County, a ~4,000-tree, 500-acre sugarbush that historically ran mid-February to mid-March (WGLT, 2023).

Forecast for Funks Grove

Updated Sep 26, 8:36 AM EDT

No freeze-thaw days in the forecast

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

  1. SunSep 27
    73°high
    53°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 53°F — trees need a hard freeze to reload. No freeze, no run.

  2. MonSep 28
    74°high
    51°low
    0h frozen
    24h thawed
    No freeze, no run

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

  3. TueSep 29
    77°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.

  4. WedSep 30
    73°high
    63°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 63°F — trees need a hard freeze to reload. No freeze, no run.

  5. ThuOct 1
    73°high
    65°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 65°F — trees need a hard freeze to reload. No freeze, no run.

  6. FriOct 2
    72°high
    60°low
    0h frozen
    20h thawed
    No freeze, no run

    Low of 60°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.

Southern Illinois reference point: Illinois Extension's 100-tap sugarbush at the Dixon Springs Agricultural Center in Simpson.

Forecast for Simpson

Updated Sep 26, 9:16 AM EDT

No freeze-thaw days in the forecast

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

  1. SunSep 27
    75°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.

  2. MonSep 28
    76°high
    50°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 50°F — trees need a hard freeze to reload. No freeze, no run.

  3. TueSep 29
    80°high
    53°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 53°F — trees need a hard freeze to reload. No freeze, no run.

  4. WedSep 30
    81°high
    63°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 63°F — trees need a hard freeze to reload. No freeze, no run.

  5. ThuOct 1
    80°high
    67°low
    0h frozen
    24h thawed
    No freeze, no run

    Low of 67°F — trees need a hard freeze to reload. No freeze, no run.

  6. FriOct 2
    80°high
    65°low
    0h frozen
    20h thawed
    No freeze, no run

    Low of 65°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 Illinois?

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 Illinois →

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

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