Frost-Free Period Length
Find longest observed contiguous frost-free daily period with explicit endpoint censoring; unlike one seasonal frost date, longest available span is not extrapolated outside coverage.
Description
A frost-free period is a consecutive run of days whose minimum temperatures meet a chosen threshold.
A frost-free period is a consecutive run of days whose minimum temperatures meet a chosen threshold. The longest observed run describes the supplied record, and censoring flags show whether that run might continue beyond the observation window.1
Find longest observed contiguous frost-free daily period with explicit endpoint censoring; unlike one seasonal frost date, longest available span is not extrapolated outside coverage.
When to use Frost-Free Period Length
Use this tool to find longest observed contiguous frost-free daily period with explicit endpoint censoring; unlike one seasonal frost date, longest available span is not extrapolated outside coverage.
Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
How to use Frost-Free Period Length and understand its results
- Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
- Enter dailyMinimumTemperaturesC, callerFrostThresholdC using the field table and calculation rules, then run the tool.
- Read longestObservedFrostFreeDays, firstLongestRunStartIndex, leftBoundaryCensored, rightBoundaryCensored. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| dailyMinimumTemperaturesC | Daily minimum temperatures c | list of number | Required |
| callerFrostThresholdC | Caller frost threshold c | number | Required |
Supply a nonempty daily minimum-temperature list in °C and a finite frost threshold. A value equal to the threshold counts as frost-free. The tool finds all maximal qualifying runs, selects the longest and resolves equal lengths in favor of the first run. It returns its length and zero-based start plus left- and right-censoring flags for runs touching the input boundaries. No qualifying days returns length zero, start −1 and both flags false.
frost-free_i = (Tmin_i ≥ threshold); longest period = maximum consecutive qualifying run Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| longestObservedFrostFreeDays | Longest observed frost free days | number |
| firstLongestRunStartIndex | First longest run start index | number |
| leftBoundaryCensored | Left boundary censored | boolean |
| rightBoundaryCensored | Right boundary censored | boolean |
{
"input": {
"dailyMinimumTemperaturesC": [
-1,
2,
3,
4,
-1
],
"callerFrostThresholdC": 0
},
"output": {
"longestObservedFrostFreeDays": 3,
"firstLongestRunStartIndex": 1,
"leftBoundaryCensored": false,
"rightBoundaryCensored": false
}
}Limitations and assumptions
The series must represent consecutive days without gaps. The longest run need not match a designated growing season or a particular spring-to-fall window. Boundary flags indicate incomplete observed duration, and the result does not estimate future frost probability.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use Last Spring Frost Date Finder: Locate last spring observed frost within caller seasonal window; -1 explicitly means no observed event and is not a validated frost-free date, calendar/hemisphere determined by caller. For a complementary task, use First Fall Frost Date Finder: Locate first fall observed frost within caller seasonal window; -1 explicitly means no observed event and is not a validated frost-free date, calendar/hemisphere determined by caller.
References
-
Frost-Free Period Length — tool.io
Similar or alternative tools
- Last Spring Frost Date Finder
Locate last spring observed frost within caller seasonal window; -1 explicitly means no observed event and is not a validated frost-free date, calendar/hemisphere determined by caller.
- First Fall Frost Date Finder
Locate first fall observed frost within caller seasonal window; -1 explicitly means no observed event and is not a validated frost-free date, calendar/hemisphere determined by caller.