ck_first_frost: First Frost Date

In climatekit: Unified Climate Indices for Temperature, Precipitation, and Drought

First Frost Date

Description

Day of year of the first autumn frost (Tmin < 0 degrees C) in each year. Hemisphere is selected by lat: in the Northern Hemisphere (lat >= 0) the search starts at July 1 (DOY 183); in the Southern Hemisphere it starts at March 1 (DOY 60), matching the autumn entry for each.

Usage

ck_first_frost(tmin, dates, lat = 50)

Arguments

tmin	Numeric vector of daily minimum temperatures (degrees C).
dates	Date vector of the same length as tmin.
lat	Numeric. Latitude in decimal degrees, used to select the hemisphere convention. Default 50 (Northern Hemisphere).

Value

A data frame with columns period, value (day of year), date (the frost date), index, and unit.

Examples

dates <- seq(as.Date("2024-07-01"), as.Date("2024-12-31"), by = "day")
set.seed(42)
tmin <- 15 - seq_along(dates) * 0.15 + rnorm(length(dates), sd = 3)
ck_first_frost(tmin, dates)

climatekit documentation built on May 9, 2026, 5:08 p.m.