Degree-Day Accumulation

Sum degree-days from daily or hourly temperature entries and a chosen base temperature for phenology or pest timing.

Updated 2026-07-09

Reviewed by Daniel Dick · 2026-07-26

Calculator

Simple average method: daily DD = max(0, ((Tmax + Tmin) / 2) − base).
Enter one day per line with maximum and minimum temperature separated by space or comma.

Enter your values and click Calculate.

What this calculator determines

Cumulative growing degree-days (GDD) from your entered daily temperatures and a base temperature.

Formula or calculation method

For each day:

daily DD = max(0, (Tmax + Tmin) ÷ 2 − base temperature)

cumulative DD = sum of daily DD across all entered days

This is the simple average (rectangle) method. Tmax must be greater than or equal to Tmin for each row.

Definitions of inputs

  • Base temperature — Lower threshold in °F below which no heat accumulation is counted (crop- or pest-specific; you choose).
  • Tmax / Tmin — Daily maximum and minimum air temperature for each day, in °F.

Worked example

Example only — not a recommendation.

Base 50 °F, one day with Tmax 72 °F and Tmin 48 °F:

  • Daily average = (72 + 48) ÷ 2 = 60 °F
  • Daily DD = max(0, 60 − 50) = 10 degree-days

Add rows for additional days to accumulate the season total.

How to interpret the result

Compare accumulated degree-days to published phenology or pest development thresholds for your crop and region. This calculator does not fetch weather data — you supply all temperatures.

Assumptions

  • Temperature entries are accurate for your site.

Limitations

  • Does not replace regional model outputs or pest-specific thresholds without verification.

Version 0.1.0 · Last updated: 2026-07-09 · Reviewed: 2026-07-26

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Disclaimer

This tool compares your inputs to static thresholds. Local site conditions, radiation, wind, and exposure duration can change actual outcomes.