Chill Hours Calculator — Three Models, From Your Own Temperature Data
Give it an hourly temperature series and a season. You get chill accumulated three ways — the simple 32–45 °F count, Utah chill units, and Dynamic-model chill portions — plotted together, because the three disagree and which one an orchard uses is a decision worth seeing the size of.
Your data
Drop your logger CSV or Excel file here
CSV, TSV and .xlsx workbooks. HOBOware and Postlad exports are recognised on sight, and most other files are read anyway. It stays on this machine — the workbook is even unzipped here, and nothing is uploaded.
Synthetic hourly air temperature for one San Joaquin Valley winter, 1 November 2025 to 28 February 2026, written by a logger on a fixed UTC-08:00 with no daylight saving. It contains multi-day tule-fog spells, clear February warm spells above 18 °C — which is where the Utah model starts deducting chill — and a deliberate 62-hour outage in mid-January, so the coverage warning is visible. Generated, not measured.
Saved projects
0 of 1Projects are stored in this browser only — never uploaded, and gone if you clear site data. Download one as a file to keep it, move it to another machine, or send it to a colleague.
Click any title, axis label, legend or note on the figure to reword it — Enter keeps it, Escape cancels, and an empty box hides the line. The numbers are not editable.
SVG is vector — scale it to any size in Illustrator, Inkscape or LaTeX without losing quality, and edit the type. Use it unless a journal insists on raster.
Options
Series
Hourly air temperature. Anything finer is averaged to hourly means first.
The three models are defined in °C. A Fahrenheit column is converted, and the figure says so.
Season
A northern season wraps the year end; a southern one does not. Dates are read in the file’s own time offset.
More options — season, models, figure
Season
0 is the most recent season the record covers, 1 the one before it.
Models
Both are computed and both are in the totals. This picks which one gets a curve.
Figure
All of that was worked out in this browser tab. Your file was not uploaded, and no request goes out while you work — open the network panel and watch, if you like.
How this tool’s arithmetic is checked — the published worked examples this tool reproduces, printed beside what it computes, with the test files that assert them.