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Ontario · maple atlas

Maple sugaring in Lambton, Ontario

Lambton is a county in Ontario. Ontario's census divisions are its counties, districts and regional municipalities. Statistics Canada's 2021 Census of Agriculture counted 39 farms reporting maple taps and 13,199 taps here. Around Sarnia, sap usually runs from February 28 to March 31. Here's the long-run pattern, 35 seasons of sap weather, and the outlook this week.
Too early to tapAbout 144 days until the usual start.
Sap starts
Feb 28
weather estimate
Season ends
Mar 31
about 4 weeks
Sap days / season
31.9
1991–2025 average
Taps, 2021
13,199
#26 of 29 in ON

Sap-flow outlook at Sarnia right now

Full Ontario forecast →

Forecast for Sarnia, ON

Updated Oct 7, 11:00 AM EDT

Off-season for now. Sap needs freezing nights, and none are in sight. Lambton's season usually opens around February 28, which is 144 days away.

No freeze-thaw days in the forecast

freeze thaw 0 °C

  1. ThuOct 8
    10° / 20°
    No refreeze forecast
  2. FriOct 9
    4° / 19°
    No refreeze forecast
  3. SatOct 10
    7° / 26°
    No refreeze forecast
  4. SunOct 11
    16° / 23°
    No refreeze forecast
  5. MonOct 12
    13° / 20°
    No refreeze forecast
  6. TueOct 13
    14° / 17°
    No refreeze forecast

Data: Environment and Climate Change Canada. Verdicts use freeze-thaw thresholds from maple field research; your woods may run a little differently.

When the sap runs

The sugaring calendar at Sarnia

Freeze-thaw weather at Sarnia peaks in the weeks of Feb 16 to Apr 6, which hold about 55% of a season's sap days. March is the busiest month. Typical dates are a weather estimate (no official season record for this province): the median of this division's own weather signals.
Typical season: Feb 28 – Mar 310246Week of Dec 1: 1.5 sap days on averageWeek of Dec 8: 1.5 sap days on averageWeek of Dec 15: 1.4 sap days on averageWeek of Dec 22: 1.1 sap days on averageWeek of Dec 29: 0.7 sap days on averageWeek of Jan 5: 1.1 sap days on averageWeek of Jan 12: 0.7 sap days on averageWeek of Jan 19: 0.7 sap days on averageWeek of Jan 26: 0.7 sap days on averageWeek of Feb 2: 1.3 sap days on averageWeek of Feb 9: 1.2 sap days on averageWeek of Feb 16: 1.9 sap days on averageWeek of Feb 23: 1.8 sap days on averageWeek of Mar 2: 2.1 sap days on averageWeek of Mar 9: 2.3 sap days on averageWeek of Mar 16: 2.7 sap days on averageWeek of Mar 23: 2.5 sap days on averageWeek of Mar 30: 2.6 sap days on averageWeek of Apr 6: 1.7 sap days on averageWeek of Apr 13: 1.0 sap days on averageWeek of Apr 20: 0.7 sap days on averageWeek of Apr 27: 0.3 sap days on averageWeek of May 4: 0.1 sap days on averageWeek of May 11: 0.1 sap days on averageWeek of May 18: 0.1 sap days on averageWeek of May 25: 0.0 sap days on averageDecJanFebMarAprMaytaps in ~Feb 28
Average number of freeze-thaw sap days in each week of the season at Sarnia, 1991–2025 (Daymet temperatures). A sap day is an overnight low under −1 °C (30.2 °F) followed by an afternoon high over +3 °C (37.4 °F). The shaded band is the typical season.

Year-to-year spread

Opening signal
Median Feb 28; the middle half of seasons fell between Feb 23 and Mar 9. Earliest Jan 31 (2017), latest Mar 15 (1996).
Closing signal
Median Mar 31; middle half between Mar 25 and Apr 7. Earliest Mar 2 (2024), latest Apr 18 (1993).
Sap days by month
Dec19%Jan11%Feb20%Mar33%Apr17%May1%

35 seasons of sap weather

Lambton seasons, 1991–2025

The best sap year at Sarnia was 2020 with 47 freeze-thaw days; the leanest was 2011 with 16. 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 days20252025: Feb 23 – Mar 28, 28 sap days2820242024: Feb 6 – Mar 2, 31 sap days3120232023: Feb 19 – Mar 20, 40 sap days4020222022: Mar 6 – Apr 4, 35 sap days3520212021: Feb 23 – Mar 21, 33 sap days3320202020: Feb 22 – Mar 26, 47 sap days4720192019: Mar 4 – Apr 4, 37 sap days3720182018: Mar 15 – Apr 15, 35 sap days3520172017: Jan 31 – Mar 5, 27 sap days2720162016: Feb 10 – Mar 13, 33 sap days3320152015: Mar 10 – Apr 5, 28 sap days2820142014: Mar 14 – Apr 17, 28 sap days2820132013: Mar 11 – Apr 8, 33 sap days3320122012: Feb 9 – Mar 11, 39 sap days3920112011: Mar 9 – Apr 3, 16 sap days1620102010: Feb 25 – Mar 31, 22 sap days2220092009: Feb 27 – Mar 31, 36 sap days3620082008: Mar 6 – Apr 6, 33 sap days3320072007: Mar 9 – Mar 21, 22 sap days2220062006: Feb 24 – Mar 29, 29 sap days2920052005: Mar 6 – Mar 29, 28 sap days2820042004: Feb 27 – Mar 24, 31 sap days3120032003: Mar 9 – Apr 13, 21 sap days2120022002: Mar 3 – Apr 7, 40 sap days4020012001: Mar 7 – Apr 5, 29 sap days2920002000: Feb 28 – Mar 7, 32 sap days3219991999: Feb 26 – Mar 28, 40 sap days4019981998: Feb 20 – Mar 25, 30 sap days3019971997: Feb 26 – Apr 1, 36 sap days3619961996: Mar 15 – Apr 11, 35 sap days3519951995: Feb 20 – Mar 27, 32 sap days3219941994: Mar 8 – Apr 8, 25 sap days2519931993: Mar 14 – Apr 18, 27 sap days2719921992: Mar 7 – Apr 7, 39 sap days3919911991: Feb 28 – Apr 4, 41 sap days41
Each bar runs from the season's opening signal to its closing signal, estimated from daily Daymet temperatures at Sarnia. Dashed lines mark the typical dates. The right column counts freeze-thaw sap days from December through May.

Maple production

Lambton in the Census of Agriculture

Statistics Canada counts the farms that report maple taps in its Census of Agriculture every five years. In 2021 it counted 39 in Lambton, with 13,199 taps; in 2016, 35 farms and 14,682 taps. Among Ontario's 29 census divisions with a published tap count, Lambton ranks 26th, and 91st of the 94 in this atlas.

Over the five years the farm count changed +11% and taps −10%. Statistics Canada cautions that 2021 and 2016 are not strictly comparable: the census-farm definition changed in 2021, and farms were assigned to their main location more strictly.

Statistics Canada doesn't publish syrup volume by census division, so the Canadian pages show farms and taps, not gallons or litres.

Lambton maple production, 2016 and 2021 (Statistics Canada, Census of Agriculture)
Census yearFarms reporting tapsTaps
20213913,199E
20163514,682
  • E Statistics Canada quality grade: use with caution.

Nearby

Neighboring maple divisions

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

About these numbers

The season dates are estimated from 35 seasons of daily high and low temperatures for the Daymet 1-km grid cell at Sarnia, the division's most populous municipality in the 2021 Census; the cell sits at 184 m (604 ft). Each day is scored with the same freeze-thaw rule as our live forecast: a sap day is an overnight low under −1 °C (30.2 °F) followed by an afternoon high over +3 °C (37.4 °F). A season's closing signal is the last sap day before accumulated warmth reaches a threshold, and the opening signal sits 35 days before that, never earlier than the first real freeze-thaw week. The rule was calibrated on 117 state-seasons of USDA-reported dates in the US and is applied here unchanged. Ontario has no official season record, so the typical dates are a weather estimate. Production figures are copied from Statistics Canada as published. Full method, the Daymet checks and the Quebec validation → Run a sugarhouse here? Put this sap forecast on your own website →

Sources · 7

  1. 1.Maple taps, Census of Agriculture, 2021 (Table 32-10-0362-01) · Statistics Canada
  2. 2.Maple taps, Census of Agriculture, 2011 and 2016 (Table 32-10-0423-01) · Statistics Canada
  3. 3.Daymet: Daily Surface Weather Data on a 1-km Grid for North America, Version 4 R1 · ORNL DAAC
  4. 4.Sap flow in sugar maple: timing and weather drivers (Frontiers in Agronomy, 2025) · de Lima Santos et al.
  5. 5.2021 Census cartographic boundary files (census divisions, population centres) · Statistics Canada
  6. 6.Population and dwelling counts, 2021 Census (Tables 98-10-0002-01 and 98-10-0011-01) · Statistics Canada
Show 1 more
  1. 7.GeoNames geographical database (CA) · GeoNames

Licences and attribution

  • Adapted from Statistics Canada, Census of Agriculture 2021 and 2016 (Tables 32-10-0362-01 and 32-10-0423-01), 2021 Census population and dwelling counts (Tables 98-10-0002-01 and 98-10-0011-01) and 2021 Census cartographic boundary files. This does not constitute an endorsement by Statistics Canada of this product.
  • Contains information licensed under the Open Government Licence – Canada.
  • Thornton, M.M., R. Shrestha, Y. Wei, P.E. Thornton, S-C. Kao, and B.E. Wilson. 2022. Daymet: Daily Surface Weather Data on a 1-km Grid for North America, Version 4 R1. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/2129
  • Place coordinates: GeoNames (geonames.org), CC BY 4.0.

FAQ

Lambton sugaring questions

When should I tap maple trees in Lambton, Ontario?
In a typical year the sap starts running around February 28 near Sarnia and the season winds down around March 31. Have your taps in a day or two before the first forecast string of nights below −1 °C and days above +3 °C. In the past 35 seasons the weather signal came as early as Jan 31 and as late as Mar 15.
How much maple syrup does Lambton produce?
Statistics Canada doesn't publish syrup volume by census division. Its 2021 Census of Agriculture counted 39 farms reporting 13,199 maple taps in Lambton, number 26 of 29 Ontario divisions with a published count.
How many sap days does Lambton get in a season?
On average 31.9 freeze-thaw sap days from December through May at Sarnia, of which about 15.4 are textbook days with a night between about −7 and −2 °C and a day between 4 and 9 °C. The best season since 1991 was 2020 (47 sap days); the leanest was 2011 (16).
Where do these dates come from?
From 35 seasons of daily high and low temperatures at Sarnia (Daymet 1-km grid), scored with the same freeze-thaw rule as our live forecast. Ontario has no official season record, so they are a weather estimate. They describe a typical year at one point in the division; your sugarbush, slope and elevation can shift them by days.

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