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.
Description
The first fall frost is the earliest frost observation inside a chosen seasonal search window.
The first fall frost is the earliest frost observation inside a chosen seasonal search window. Selecting the window explicitly allows different hemispheres and local definitions of fall to use the same comparison rule.1
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.
When to use First Fall Frost Date Finder
Use this tool to 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.
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 First Fall Frost Date Finder 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, seasonStartIndex, seasonEndIndexInclusive, callerFrostThresholdC using the field table and calculation rules, then run the tool.
- Read observedFrostFound, frostDayIndex. 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 |
| seasonStartIndex | Season start index | integer | Required |
| seasonEndIndexInclusive | Season end index inclusive | integer | Required |
| callerFrostThresholdC | Caller frost threshold c | number | Required |
Enter daily minimum temperatures in °C, a finite frost threshold and nonnegative integer start and end indices within the supplied series, with start at most end. The tool scans that inclusive window for the first temperature strictly below the threshold. It returns the zero-based index and a found flag; no qualifying observation returns index −1 and false.
frost_i = (Tmin_i < threshold); first index = min qualifying i in the inclusive search window Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| observedFrostFound | Observed frost found | boolean |
| frostDayIndex | Frost day index | number |
{
"input": {
"dailyMinimumTemperaturesC": [
2,
-1,
3,
-2
],
"seasonStartIndex": 1,
"seasonEndIndexInclusive": 3,
"callerFrostThresholdC": 0
},
"output": {
"observedFrostFound": true,
"frostDayIndex": 1
}
}Limitations and assumptions
Calendar dates and the definition of fall are supplied indirectly by your index window; no seasonal boundary is built in. Equality with the threshold is not a frost. A false flag describes only the supplied observations and does not establish that a frost-free season continues indefinitely.
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 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.
References
-
First Fall Frost Date Finder — 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.
- 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.