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Iowa · county maple atlas

Maple sugaring in Dubuque County, Iowa

Dubuque County had 8 maple operations in the 2022 Census (tap totals withheld). Around Dubuque, sap usually runs from February 26 to March 29. Here's the long-run pattern, 36 seasons of sap weather, and the outlook this week.
Too early to tapAbout 143 days until the usual start.
Sap starts
Feb 26
weather estimate
Season ends
Mar 29
about 4 weeks
Sap days / season
34.7
1991–2026 average
Taps, 2022
withheld
8 farms

Sap-flow outlook at Dubuque right now

Full Iowa forecast →

Forecast for Dubuque, IA

Updated Oct 6, 7:46 AM EDT

Off-season for now. Sap needs freezing nights, and none are in sight. Dubuque County's season usually opens around February 26, which is 143 days away.

No freeze-thaw days in the forecast

freeze thaw 32°F

  1. WedOct 7
    56° / 75°

    0h below · 24h above

    No refreeze forecast
  2. ThuOct 8
    51° / 67°

    0h below · 24h above

    No refreeze forecast
  3. FriOct 9
    48° / 70°

    0h below · 24h above

    No refreeze forecast
  4. SatOct 10
    56° / 76°

    0h below · 24h above

    No refreeze forecast
  5. SunOct 11
    61° / 78°

    0h below · 24h above

    No refreeze forecast
  6. MonOct 12
    59° / 70°
    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 Dubuque

Freeze-thaw weather at Dubuque peaks in the weeks of Feb 16 to Mar 30, which hold about 51% of a season's sap days. March is the busiest month. Note: USDA publishes no season dates for Iowa, so the typical dates here are the raw weather signal. In neighboring states with USDA records, producers reported their seasons running one to three weeks later than this rule.
Typical season: Feb 26 – Mar 290246Week of Dec 1: 1.6 sap days on averageWeek of Dec 8: 1.9 sap days on averageWeek of Dec 15: 1.5 sap days on averageWeek of Dec 22: 1.4 sap days on averageWeek of Dec 29: 0.9 sap days on averageWeek of Jan 5: 1.4 sap days on averageWeek of Jan 12: 0.9 sap days on averageWeek of Jan 19: 0.7 sap days on averageWeek of Jan 26: 1.1 sap days on averageWeek of Feb 2: 1.4 sap days on averageWeek of Feb 9: 1.5 sap days on averageWeek of Feb 16: 2.1 sap days on averageWeek of Feb 23: 2.2 sap days on averageWeek of Mar 2: 2.5 sap days on averageWeek of Mar 9: 2.8 sap days on averageWeek of Mar 16: 3.2 sap days on averageWeek of Mar 23: 3.1 sap days on averageWeek of Mar 30: 1.9 sap days on averageWeek of Apr 6: 1.5 sap days on averageWeek of Apr 13: 0.9 sap days on averageWeek of Apr 20: 0.2 sap days on averageWeek of Apr 27: 0.0 sap days on averageWeek of May 4: 0.1 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 ~Feb 26
Average number of freeze-thaw sap days in each week of the season at Dubuque, 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 Feb 26; the middle half of seasons fell between Feb 20 and Mar 5. Earliest Feb 2 (2024), latest Mar 18 (2018).
Closing signal
Median Mar 29; middle half between Mar 24 and Apr 4. Earliest Mar 5 (2000), latest Apr 20 (2018).
Sap days by month
Dec20%Jan13%Feb20%Mar36%Apr11%May0%

36 seasons of sap weather

Dubuque County seasons, 1991–2026

The best sap year at Dubuque was 2002 with 52 freeze-thaw days; the leanest was 2010 with 15. 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: Feb 5 – Mar 12, 43 sap days4320252025: Feb 12 – Mar 17, 34 sap days3420242024: Feb 2 – Mar 8, 43 sap days4320232023: Mar 3 – Apr 7, 43 sap days4320222022: Mar 6 – Apr 9, 45 sap days4520212021: Feb 22 – Mar 29, 34 sap days3420202020: Feb 28 – Apr 2, 45 sap days4520192019: Mar 3 – Apr 1, 36 sap days3620182018: Mar 18 – Apr 20, 50 sap days5020172017: Feb 15 – Mar 22, 28 sap days2820162016: Feb 18 – Mar 21, 31 sap days3120152015: Mar 7 – Mar 29, 19 sap days1920142014: Mar 12 – Apr 16, 29 sap days2920132013: Mar 15 – Apr 4, 35 sap days3520122012: Feb 10 – Mar 11, 41 sap days4120112011: Mar 5 – Apr 6, 26 sap days2620102010: Feb 28 – Mar 30, 15 sap days1520092009: Feb 18 – Mar 21, 26 sap days2620082008: Mar 13 – Apr 4, 28 sap days2820072007: Feb 19 – Mar 21, 40 sap days4020062006: Feb 26 – Mar 27, 44 sap days4420052005: Feb 28 – Mar 28, 38 sap days3820042004: Feb 22 – Mar 24, 35 sap days3520032003: Feb 25 – Apr 1, 34 sap days3420022002: Feb 23 – Mar 28, 52 sap days5220012001: Mar 10 – Apr 2, 23 sap days2320002000: Feb 28 – Mar 5, 37 sap days3719991999: Feb 24 – Mar 27, 35 sap days3519981998: Feb 20 – Mar 25, 23 sap days2319971997: Feb 26 – Mar 31, 35 sap days3519961996: Mar 8 – Apr 11, 40 sap days4019951995: Feb 18 – Mar 25, 25 sap days2519941994: Mar 4 – Apr 8, 36 sap days3619931993: Mar 14 – Apr 18, 28 sap days2819921992: Feb 21 – Mar 28, 40 sap days4019911991: Feb 26 – Apr 1, 33 sap days33
Each bar runs from the season's opening signal to its closing signal, estimated from daily temperatures at Dubuque. Dashed lines mark the typical dates. The right column counts freeze-thaw sap days from December through May.

Maple production

Dubuque County in the Census of Agriculture

USDA counts maple operations every five years. In Dubuque County the 2022 Census found 8 farms making syrup (+300% since 2017).

Dubuque County maple production, 2017 and 2022 (USDA Census of Agriculture)
Census yearFarmsTapsGallons of syrupGal / tap
20228withheldwithheld—
20172withheldwithheld—

“Withheld” means USDA suppressed the figure to avoid disclosing data for individual operations; the farm count is still published.

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 Dubuque (673ft), 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. 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 — Iowa, 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

Dubuque County sugaring questions

When should I tap maple trees in Dubuque County, Iowa?
In a typical year the sap starts running around February 26 near Dubuque and the season winds down around March 29. 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 2 and as late as Mar 18.
How much maple syrup does Dubuque County produce?
The 2022 Census of Agriculture counted 8 maple operations in Dubuque County; USDA withheld the county's tap and gallon totals to avoid disclosing individual farms.
How many sap days does Dubuque County get in a season?
On average 34.7 freeze-thaw sap days from December through May at Dubuque, of which about 13.7 are textbook days with a night in the 20s and a day in the 40s. The best season since 1991 was 2002 (52 sap days); the leanest was 2010 (15).
Where do these dates come from?
From 36 seasons of daily high and low temperatures at Dubuque (PRISM 4-km grid), scored with the same freeze-thaw rule as our live forecast, then calibrated against USDA's reported season dates for Iowa. 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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