icclim is a Python library to compute climate indices. icclim name stands for index, calculation, climate.

Installation

From conda-forge (recommended): conda install -c conda-forge icclim.

From pypi: pip install icclim.

From sources:

• Clone the repository git clone https://github.com/cerfacs-globc/icclim.git
• Install icclim pip install .

Compatibility

icclim is designed to be highly compatible across the Python scientific ecosystem:

• Python: Supports Python 3.10 and above.
• Backward Compatibility: Supports older stable versions (e.g., numpy>=1.21, xarray>=2022.6, xclim>=0.45).
• Bleeding Edge: Fully verified and recommended to run on the latest major versions, including Zarr 3.x, Pandas 3.x, and Xarray 2026.x.

For production environments, we recommend keeping your dependencies updated to their latest stable releases to benefit from the latest optimizations and features.

How to use icclim

Let's count the number of days above 25°C for each year, which corresponds to the index SU, from a tasmax variable scattered in multiple netcdf files.

SU is one of the many index that can be computed with icclim. See the documentation to explore what other index you can compute with icclim.

import icclim

summer_days = icclim.su(
    "netcdf_files/tasmax_1990-2100.nc", out_file="summer_days.nc"
)

For more examples on how to use icclim, see icclim's How to ... documentation or our notebooks.

Who use icclim

icclim is part of C4I platform backend and is integrated in CLIPC Portal. icclim is also used by independent researchers.

Who made icclim

icclim has always been an open source project and was successfully made thanks to the joint effort of all its contributors. The lead development is made at CERFACS, a research institution located in Toulouse, France.

Grants

This open-source project has been possible thanks to funding by the European Commission projects:

• FP7 CLIPC (2013-2016)
• FP7 IS-ENES2 (2013-2017)
• H2020 EUDAT2020 (2015-2018)
• H2020 IS-ENES3 (2019-2023)

This project also receives funding from Agence Nationale de la Recherche - France 2030 as part of the PEPR TRACCS programme under grant number ANR-22-EXTR-0003 (PC2-INVEST 2024-2032).

The beautiful icclim logo is a creation of Carole Petetin and has been funded by the H2020 IS-ENES3 project grant agreement No 824084 (2019-2023).

Indices

For a detailed description of each ECA&D index, please visit: https://www.ecad.eu/documents/atbd.pdf