Agriculture climate layer

First Autumn Frost Map

Explore the average date of the first modeled autumn frost during 2011–2025. The map helps compare the typical timing of the first modeled freezing day in autumn.

Explore Interactive Map General methodology
Source
ERA5-Land
Climate period
2011–2025 conditional frost-date average
Representation
Calendar date

What this map shows

Each value is the conditional mean date of the first valid local day below 0 °C in the second half of the agricultural year. Only years in which an autumn frost occurred contribute to the average date.

It is not a forecast, a guaranteed harvest deadline, or a frost probability percentile. The average does not show the earliest autumn frost within the period.

How it is calculated

MetriClima aggregates hourly ERA5-Land temperature into local solar days, finds the first daily minimum below 0 °C in the second agricultural half, and averages those dates across valid years in which an autumn frost occurred.

Hemisphere-specific agricultural years keep autumn in the second half, and dates use the same normalized 365-day calendar as the other growing-season layers.

Data source

MetriClima processes ERA5-Land surface data on the 0.1° latitude–longitude download grid. The physical spacing of this geographic grid varies with latitude. ERA5-Land is a land-surface reanalysis dataset providing consistent hourly climate variables.

This layer uses local-day minimum 2 m air temperature with daily and annual completeness checks. Valid years without an autumn frost are tracked separately rather than assigned a false calendar date.

Provider
Copernicus Climate Change Service (C3S), produced by ECMWF

Climate period and representation

2011–2025 conditional frost-date average

The displayed date is averaged only over valid years in which an autumn frost occurred.

Calendar date

Average dates are displayed in 15-day map bands on a normalized 365-day agricultural calendar.

How to interpret the map

A later mapped date indicates a later average first autumn frost among years in which autumn frost occurred. Individual years can experience the first frost much earlier or later than the mapped average.

For climatic context relevant to crop planning, combine this layer with maturity requirements, growing-season heat, current forecasts, and local frost records.

Applications

  • Comparing autumn frost timing between locations
  • Providing climatic context for harvest, crop maturity, and season-extension planning
  • Providing frost-timing context for horticulture and viticulture
  • Understanding the closing boundary of the frost-free period

Limitations

  • The conditional mean excludes frost-free years and does not communicate occurrence probability by itself.
  • A gridded 2 m threshold cannot fully represent canopy, fruit, or ground-surface temperature.
  • Local terrain, exposure, water bodies, and urbanization can shift actual frost timing relative to the grid-cell estimate.

Explore this map by country

Open First Autumn Frost for a country to start the same interactive map focused on that geography.

Africa (54)
Asia (50)
Australia (14)
Europe (47)
North America (24)
South America (12)