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Iowa · county maple atlas

Maple sugaring in Floyd County, Iowa

Floyd County had 5 maple operations and 242 taps in the 2022 Census, number 5 in Iowa. Around Charles City, sap usually runs from March 4 to April 2. Here's the long-run pattern, 36 seasons of sap weather, and the outlook this week.
Too early to tapAbout 149 days until the usual start.
Sap starts
Mar 4
weather estimate
Season ends
Apr 2
about 4 weeks
Sap days / season
33.5
1991–2026 average
Taps, 2022
242
#5 of 32 in IA

Sap-flow outlook at Charles City right now

Full Iowa forecast →

Forecast for Charles City, IA

Updated Oct 6, 9:06 AM EDT

Off-season for now. Sap needs freezing nights, and none are in sight. Floyd County's season usually opens around March 4, which is 149 days away.

No freeze-thaw days in the forecast

freeze thaw 32°F

  1. WedOct 7
    52° / 73°

    0h below · 24h above

    No refreeze forecast
  2. ThuOct 8
    48° / 67°

    0h below · 24h above

    No refreeze forecast
  3. FriOct 9
    46° / 70°

    0h below · 24h above

    No refreeze forecast
  4. SatOct 10
    56° / 77°

    0h below · 24h above

    No refreeze forecast
  5. SunOct 11
    60° / 76°

    0h below · 24h above

    No refreeze forecast
  6. MonOct 12
    57° / 66°
    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 Charles City

Freeze-thaw weather at Charles City peaks in the weeks of Mar 2 to Apr 6, which hold about 44% 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: Mar 4 – Apr 20246Week of Dec 1: 1.9 sap days on averageWeek of Dec 8: 1.7 sap days on averageWeek of Dec 15: 1.4 sap days on averageWeek of Dec 22: 1.3 sap days on averageWeek of Dec 29: 0.8 sap days on averageWeek of Jan 5: 1.0 sap days on averageWeek of Jan 12: 0.8 sap days on averageWeek of Jan 19: 0.7 sap days on averageWeek of Jan 26: 1.0 sap days on averageWeek of Feb 2: 1.1 sap days on averageWeek of Feb 9: 1.3 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: 2.0 sap days on averageWeek of Mar 9: 2.6 sap days on averageWeek of Mar 16: 2.9 sap days on averageWeek of Mar 23: 2.9 sap days on averageWeek of Mar 30: 2.6 sap days on averageWeek of Apr 6: 1.9 sap days on averageWeek of Apr 13: 1.2 sap days on averageWeek of Apr 20: 0.7 sap days on averageWeek of Apr 27: 0.2 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 ~Mar 4
Average number of freeze-thaw sap days in each week of the season at Charles City, 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 4; the middle half of seasons fell between Feb 25 and Mar 9. Earliest Feb 6 (2024), latest Mar 23 (2013).
Closing signal
Median Apr 2; middle half between Mar 25 and Apr 7. Earliest Mar 5 (2000), latest Apr 25 (2013).
Sap days by month
Dec20%Jan12%Feb17%Mar34%Apr17%May0%

36 seasons of sap weather

Floyd County seasons, 1991–2026

The best sap year at Charles City was 2002 with 59 freeze-thaw days; the leanest was 2010 with 12. 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 17 – Mar 24, 40 sap days4020252025: Feb 19 – Mar 26, 44 sap days4420242024: Feb 6 – Mar 12, 53 sap days5320232023: Mar 7 – Apr 7, 42 sap days4220222022: Mar 8 – Apr 10, 46 sap days4620212021: Feb 23 – Mar 21, 38 sap days3820202020: Mar 4 – Apr 7, 46 sap days4620192019: Mar 4 – Apr 3, 25 sap days2520182018: Mar 23 – Apr 21, 43 sap days4320172017: Feb 21 – Mar 23, 20 sap days2020162016: Feb 26 – Mar 23, 32 sap days3220152015: Feb 25 – Mar 29, 18 sap days1820142014: Mar 15 – Apr 18, 30 sap days3020132013: Mar 23 – Apr 25, 31 sap days3120122012: Feb 11 – Mar 11, 39 sap days3920112011: Mar 6 – Apr 6, 25 sap days2520102010: Mar 5 – Mar 30, 12 sap days1220092009: Mar 4 – Apr 8, 29 sap days2920082008: Mar 16 – Apr 6, 18 sap days1820072007: Feb 23 – Mar 21, 37 sap days3720062006: Mar 2 – Mar 27, 40 sap days4020052005: Mar 1 – Apr 3, 39 sap days3920042004: Feb 23 – Mar 24, 36 sap days3620032003: Feb 25 – Mar 31, 34 sap days3420022002: Mar 7 – Apr 7, 59 sap days5920012001: Mar 14 – Apr 2, 14 sap days1420002000: Feb 28 – Mar 5, 39 sap days3919991999: Feb 26 – Mar 27, 36 sap days3619981998: Mar 20 – Mar 25, 17 sap days1719971997: Mar 10 – Apr 14, 33 sap days3319961996: Mar 10 – Apr 11, 35 sap days3519951995: Feb 26 – Apr 2, 29 sap days2919941994: Mar 7 – Apr 8, 37 sap days3719931993: Mar 19 – Apr 21, 20 sap days2019921992: Mar 3 – Apr 5, 36 sap days3619911991: Mar 1 – Apr 1, 34 sap days34
Each bar runs from the season's opening signal to its closing signal, estimated from daily temperatures at Charles City. Dashed lines mark the typical dates. The right column counts freeze-thaw sap days from December through May.

Maple production

Floyd County in the Census of Agriculture

USDA counts maple operations every five years. In Floyd County the 2022 Census found 5 farms making syrup, with taps null and syrup output null over the same five years. That works out to about 0.11 gallons of syrup per tap in 2022. Among the 385 counties in this atlas, Floyd County ranks 338 by taps.

Floyd County maple production, 2017 and 2022 (USDA Census of Agriculture)
Census yearFarmsTapsGallons of syrupGal / tap
20225242270.11
2017000—

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 Charles City (1,037ft), 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

Floyd County sugaring questions

When should I tap maple trees in Floyd County, Iowa?
In a typical year the sap starts running around March 4 near Charles City and the season winds down around April 2. 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 6 and as late as Mar 23.
How much maple syrup does Floyd County produce?
The 2022 Census of Agriculture counted 5 maple operations in Floyd County with 242 taps producing 27 gallons of syrup, ranking 5 of 32 Iowa's counties with published tap counts.
How many sap days does Floyd County get in a season?
On average 33.5 freeze-thaw sap days from December through May at Charles City, of which about 11 are textbook days with a night in the 20s and a day in the 40s. The best season since 1991 was 2002 (59 sap days); the leanest was 2010 (12).
Where do these dates come from?
From 36 seasons of daily high and low temperatures at Charles City (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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