When to tap maple trees in Iowa
Maple season in Iowa usually opens mid-to-late February and winds down March, once buds begin to break. Here's the long-run pattern, the year-by-year record, and what the forecast says right now.
- Opens
- mid-to-late February
- Closes
- March, once buds begin to break
Forecast for Decorah
Updated Sep 26, 6:31 AM EDT
No freeze-thaw days in the forecast
Blue = below 32°F · Amber = thaw · dashed line = freezing
- SunSep 27No freeze, no run66°high55°low0h frozen
24h thawed - MonSep 28No freeze, no run70°high56°low0h frozen
24h thawed - TueSep 29No freeze, no run67°high55°low0h frozen
24h thawed - WedSep 30No freeze, no run68°high58°low0h frozen
24h thawed - ThuOct 1No freeze, no run67°high57°low0h frozen
24h thawed - FriOct 2No freeze, no run65°high51°low0h frozen
20h thawed
Data: National Weather Service. Verdicts use freeze-thaw thresholds from maple field research; your woods may run a little differently.
Sap runs on a temperature swing, not a date. A night below freezing loads the tree; a day above freezing pushes sap out of the taphole. Field research treats a low under about 30°F followed by a high over about 37°F as a real freeze-thaw day, and big runs almost always come on days like that.
So watch the 10-day forecast. When you see a string of nights in the 20s and afternoons in the 40s, get your taps in a day or two ahead. Tap south-facing slopes first — they warm and run earlier.
No NASS season data for Iowa. ISU Extension (2026): sap collection typically runs mid-February through early March. An older ISU page (reviewed 2019): collection usually begins in late February or early March and lasts about three weeks. Stop when buds break and nights stay warm.
Seasons are shifting. In New England and New York, the sugaring season now begins about 8 days earlier and ends about 11 days earlier than it did 40 years earlier, leaving it roughly 3 days (about 10%) shorter, according to UVM Proctor Maple Research Center survey records analyzed in 2007.
Plan your season
Sources
- A Sweet Science: The Basics of Making Maple Syrup — Iowa State University Extension and Outreach
- Maple Syrup Production — Iowa State University Extension and Outreach
- USDA 2022 Census of Agriculture, County Data — Table 37. Maple Syrup: 2022 and 2017 (Iowa) — USDA National Agricultural Statistics Service
- Statement of Timothy D. Perkins, Ph.D., Director, UVM Proctor Maple Research Center — Global Warming Mountaintop 'Summit': Economic Impacts on New England (June 4, 2007) — U.S. House Select Committee on Energy Independence and Global Warming
Common questions
- When is maple syrup season in Iowa?
- Usually from mid-to-late February to March, once buds begin to break. The exact start moves by weeks from year to year with the weather.
- When should I tap my trees in Iowa?
- Tap just before the first good run: when the forecast shows nights below freezing and days climbing to around 40°F. Tapholes dry up within 6 to 10 weeks, so tapping far too early can cost you the late runs.
- What weather makes sap run?
- Freezing nights and thawing days. Field research counts a freeze-thaw day as a low under about 30°F and a high over about 37°F; nights in the 20s and days in the 40s are the classic sap days.
Get a heads-up when Iowa's sap will run
LuckySap checks the forecast for your trees and can ping you the night before a strong sap day — then keeps every collection and boil in one season log. Free on iPhone.
