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Maine · county maple atlas

Maple sugaring in Knox County, Maine

Knox County had 9 maple operations and 3,160 taps in the 2022 Census. Around Rockland, sap usually runs from March 1 to April 8. Here's the long-run pattern, 36 seasons of sap weather, and the outlook this week.
Too early to tapAbout 146 days until the usual start.
Sap starts
Mar 1
typical year
Season ends
Apr 8
about 5 weeks
Sap days / season
40.4
1991–2026 average
Taps, 2022
3,160
#13 of 16 in ME

Sap-flow outlook at Rockland right now

Full Maine forecast →

Forecast for Rockland, ME

Updated Oct 6, 6:54 AM EDT

No freeze-thaw days in the forecast

freeze thaw 32°F

  1. WedOct 7
    35° / 58°

    0h below · 24h above

    No refreeze forecast
  2. ThuOct 8
    53° / 66°

    0h below · 24h above

    No refreeze forecast
  3. FriOct 9
    47° / 62°

    0h below · 24h above

    No refreeze forecast
  4. SatOct 10
    45° / 60°

    0h below · 24h above

    No refreeze forecast
  5. SunOct 11
    45° / 61°

    0h below · 24h above

    No refreeze forecast
  6. MonOct 12
    52° / 65°
    No refreeze forecast

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

When the sap runs

The sugaring calendar at Rockland

Freeze-thaw weather at Rockland peaks in the weeks of Mar 2 to Apr 6, which hold about 37% of a season's sap days. March is the busiest month.
Typical season: Mar 1 – Apr 80246Week of Dec 1: 2.1 sap days on averageWeek of Dec 8: 2.3 sap days on averageWeek of Dec 15: 2.2 sap days on averageWeek of Dec 22: 1.9 sap days on averageWeek of Dec 29: 1.9 sap days on averageWeek of Jan 5: 1.5 sap days on averageWeek of Jan 12: 1.4 sap days on averageWeek of Jan 19: 1.1 sap days on averageWeek of Jan 26: 1.3 sap days on averageWeek of Feb 2: 1.4 sap days on averageWeek of Feb 9: 2.0 sap days on averageWeek of Feb 16: 1.8 sap days on averageWeek of Feb 23: 1.7 sap days on averageWeek of Mar 2: 2.1 sap days on averageWeek of Mar 9: 2.6 sap days on averageWeek of Mar 16: 2.6 sap days on averageWeek of Mar 23: 2.9 sap days on averageWeek of Mar 30: 2.3 sap days on averageWeek of Apr 6: 2.5 sap days on averageWeek of Apr 13: 1.4 sap days on averageWeek of Apr 20: 0.9 sap days on averageWeek of Apr 27: 0.4 sap days on averageWeek of May 4: 0.0 sap days on averageWeek of May 11: 0.0 sap days on averageWeek of May 18: 0.0 sap days on averageWeek of May 25: 0.0 sap days on averageDecJanFebMarAprMaytaps in ~Mar 1
Average number of freeze-thaw sap days in each week of the season at Rockland, 1991–2026. A sap day is an overnight low under 30.2 °F followed by an afternoon high over 37.4 °F. The shaded band is the typical season.

Year-to-year spread

Opening signal
Median Mar 10; the middle half of seasons fell between Mar 1 and Mar 15. Earliest Feb 16 (2012), latest Mar 22 (2015).
Closing signal
Median Apr 12; middle half between Apr 2 and Apr 16. Earliest Mar 17 (2012), latest Apr 21 (2001).
Sap days by month
Dec23%Jan16%Feb17%Mar27%Apr17%May0%

36 seasons of sap weather

Knox County seasons, 1991–2026

The best sap year at Rockland was 2020 with 54 freeze-thaw days; the leanest was 2015 with 30. Seasons that start early tend to end early too: the trees run on the swing between freezing nights and mild days, and heat ends it.
JanFebMarAprMaysap days20262026: Mar 9 – Apr 12, 37 sap days3720252025: Mar 11 – Apr 11, 32 sap days3220242024: Mar 5 – Apr 4, 36 sap days3620232023: Feb 24 – Mar 31, 49 sap days4920222022: Feb 25 – Mar 31, 38 sap days3820212021: Mar 3 – Apr 4, 35 sap days3520202020: Mar 1 – Apr 1, 54 sap days5420192019: Mar 16 – Apr 18, 40 sap days4020182018: Mar 9 – Apr 12, 47 sap days4720172017: Mar 6 – Apr 4, 42 sap days4220162016: Feb 23 – Mar 28, 45 sap days4520152015: Mar 22 – Apr 20, 30 sap days3020142014: Mar 17 – Apr 19, 31 sap days3120132013: Mar 7 – Apr 7, 44 sap days4420122012: Feb 16 – Mar 17, 39 sap days3920112011: Mar 14 – Apr 16, 36 sap days3620102010: Feb 23 – Mar 28, 37 sap days3720092009: Mar 14 – Apr 15, 35 sap days3520082008: Mar 15 – Apr 17, 39 sap days3920072007: Mar 15 – Apr 15, 47 sap days4720062006: Feb 27 – Mar 31, 39 sap days3920052005: Mar 12 – Apr 16, 44 sap days4420042004: Mar 17 – Apr 18, 46 sap days4620032003: Mar 19 – Apr 19, 33 sap days3320022002: Mar 6 – Apr 8, 50 sap days5020012001: Mar 20 – Apr 21, 35 sap days3520002000: Feb 27 – Apr 2, 42 sap days4219991999: Mar 2 – Mar 28, 50 sap days5019981998: Feb 24 – Mar 26, 42 sap days4219971997: Mar 18 – Apr 16, 43 sap days4319961996: Mar 14 – Apr 5, 32 sap days3219951995: Mar 11 – Apr 12, 44 sap days4419941994: Mar 10 – Apr 12, 37 sap days3719931993: Mar 17 – Apr 19, 33 sap days3319921992: Mar 16 – Apr 17, 46 sap days4619911991: Feb 27 – Apr 2, 45 sap days45
Each bar runs from the season's opening signal to its closing signal, estimated from daily temperatures at Rockland. Dashed lines mark the typical dates. The right column counts freeze-thaw sap days from December through May.

Maple production

Knox County in the Census of Agriculture

USDA counts maple operations every five years. In Knox County the 2022 Census found 9 farms making syrup (+50% since 2017), with taps -32% and syrup output -43% over the same five years. That works out to about 0.10 gallons of syrup per tap in 2022 (0.12 in 2017). Among the 385 counties in this atlas, Knox County ranks 224 by taps.

Knox County maple production, 2017 and 2022 (USDA Census of Agriculture)
Census yearFarmsTapsGallons of syrupGal / tap
202293,1603080.10
201764,6375370.12

Nearby

Neighboring maple counties

Distances are between reference towns; typical dates are each county's own estimate.

About these numbers

The season dates are estimated from 36 seasons of daily high and low temperatures for the PRISM 4-km grid cell at Rockland (66ft), scored with the same freeze-thaw rule as our live forecast: a sap day is an overnight low under 30.2 °F followed by an afternoon high over 37.4 °F. Each season's closing signal is the last sap day before accumulated warmth reaches a threshold, and the opening signal sits five weeks before that, never earlier than the first real freeze-thaw week. Tested against 117 state-seasons of USDA-reported dates, the rule lands within 5.5 days of the reported close and 6.6 days of the reported opening on average, and the typical dates shown here are scaled to Maine's USDA record (12 years). Production figures are copied from the Census as published. Full method, calibration tables and the downloadable dataset →

Sources · 6

  1. 1.2022 Census of Agriculture, County Level Data — Maine, Table 37: Maple Syrup, 2022 and 2017 · USDA National Agricultural Statistics Service
  2. 2.PRISM daily temperature grids (AN81d, 4 km), accessed 2026-10-05 · PRISM Group, Oregon State University, https://prism.oregonstate.edu
  3. 3.Applied Climate Information System (ACIS) web services · NOAA Regional Climate Centers
  4. 4.USDA NASS maple syrup reports — approximate average season opened and closed dates, 2011–2022 · USDA National Agricultural Statistics Service (mirrored by the University of Vermont)
  5. 5.Sap flow in sugar maple: timing and weather drivers (Frontiers in Agronomy, 2025) · de Lima Santos et al.
  6. 6.GeoNames gazetteer (cities500), CC BY 4.0 · GeoNames

FAQ

Knox County sugaring questions

When should I tap maple trees in Knox County, Maine?
In a typical year the sap starts running around March 1 near Rockland and the season winds down around April 8. Have your taps in a day or two before the first forecast string of freezing nights and 40 °F days. In the past 36 seasons the weather signal came as early as Feb 16 and as late as Mar 22.
How much maple syrup does Knox County produce?
The 2022 Census of Agriculture counted 9 maple operations in Knox County with 3,160 taps producing 308 gallons of syrup, ranking 13 of 16 Maine's counties with published tap counts.
How many sap days does Knox County get in a season?
On average 40.4 freeze-thaw sap days from December through May at Rockland, of which about 17.3 are textbook days with a night in the 20s and a day in the 40s. The best season since 1991 was 2020 (54 sap days); the leanest was 2015 (30).
Where do these dates come from?
From 36 seasons of daily high and low temperatures at Rockland (PRISM 4-km grid), scored with the same freeze-thaw rule as our live forecast, then calibrated against USDA's reported season dates for Maine. They describe a typical year at one point in the county; your sugarbush, slope and elevation can shift them by days.

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