def heat_wave_frequency(tasmin, tasmax, thresh_tasmin='22.0 degC', thresh_tasmax='30 degC',
                        window=3, freq='YS'):
    # Dev note : we should decide if it is deg K or C
    r"""Heat wave frequency

    Number of heat waves over a given period. A heat wave is defined as an event
    where the minimum and maximum daily temperature both exceeds specific thresholds
    over a minimum number of days.

    Parameters
    ----------

    tasmin : xarrray.DataArray
      Minimum daily temperature [℃] or [K]
    tasmax : xarrray.DataArray
      Maximum daily temperature [℃] or [K]
    thresh_tasmin : str
      The minimum temperature threshold needed to trigger a heatwave event [℃] or [K]. Default : '22 degC'
    thresh_tasmax : str
      The maximum temperature threshold needed to trigger a heatwave event [℃] or [K]. Default : '30 degC'
    window : int
      Minimum number of days with temperatures above thresholds to qualify as a heatwave.
    freq : str, optional
      Resampling frequency

    Returns
    -------
    xarray.DataArray
      Number of heatwave at the wanted frequency

    Notes
    -----
    The thresholds of 22° and 25°C for night temperatures and 30° and 35°C for day temperatures were selected by
    Health Canada professionals, following a temperature–mortality analysis. These absolute temperature thresholds
    characterize the occurrence of hot weather events that can result in adverse health outcomes for Canadian
    communities (Casati et al., 2013).

    In Robinson (2001), the parameters would be `thresh_tasmin=27.22, thresh_tasmax=39.44, window=2` (81F, 103F).

    References
    ----------
    Casati, B., A. Yagouti, and D. Chaumont, 2013: Regional Climate Projections of Extreme Heat Events in Nine Pilot
    Canadian Communities for Public Health Planning. J. Appl. Meteor. Climatol., 52, 2669–2698,
    https://doi.org/10.1175/JAMC-D-12-0341.1

    Robinson, P.J., 2001: On the Definition of a Heat Wave. J. Appl. Meteor., 40, 762–775,
    https://doi.org/10.1175/1520-0450(2001)040<0762:OTDOAH>2.0.CO;2
    """
    thresh_tasmax = utils.convert_units_to(thresh_tasmax, tasmax)
    thresh_tasmin = utils.convert_units_to(thresh_tasmin, tasmin)

    cond = (tasmin > thresh_tasmin) & (tasmax > thresh_tasmax)
    group = cond.resample(time=freq)
    return group.apply(rl.windowed_run_events, window=window, dim='time')
r"""Heat wave frequency

    Number of heat waves over a given period. A heat wave is defined as an event
    where the minimum and maximum daily temperature both exceeds specific thresholds
    over a minimum number of days.

    Parameters
    ----------

    tasmin : xarrray.DataArray
      Minimum daily temperature [℃] or [K]
    tasmax : xarrray.DataArray
      Maximum daily temperature [℃] or [K]
    thresh_tasmin : str
      The minimum temperature threshold needed to trigger a heatwave event [℃] or [K]. Default : '22 degC'
    thresh_tasmax : str
      The maximum temperature threshold needed to trigger a heatwave event [℃] or [K]. Default : '30 degC'
    window : int
      Minimum number of days with temperatures above thresholds to qualify as a heatwave.
    freq : str, optional
      Resampling frequency

    Returns
    -------
    xarray.DataArray
      Number of heatwave at the wanted frequency

    Notes
    -----
    The thresholds of 22° and 25°C for night temperatures and 30° and 35°C for day temperatures were selected by
    Health Canada professionals, following a temperature–mortality analysis. These absolute temperature thresholds
    characterize the occurrence of hot weather events that can result in adverse health outcomes for Canadian
    communities (Casati et al., 2013).

    In Robinson (2001), the parameters would be `thresh_tasmin=27.22, thresh_tasmax=39.44, window=2` (81F, 103F).

    References
    ----------
    Casati, B., A. Yagouti, and D. Chaumont, 2013: Regional Climate Projections of Extreme Heat Events in Nine Pilot
    Canadian Communities for Public Health Planning. J. Appl. Meteor. Climatol., 52, 2669–2698,
    https://doi.org/10.1175/JAMC-D-12-0341.1

    Robinson, P.J., 2001: On the Definition of a Heat Wave. J. Appl. Meteor., 40, 762–775,
    https://doi.org/10.1175/1520-0450(2001)040<0762:OTDOAH>2.0.CO;2