def et_adjustment(ws):
    """
    Given an array of weather stations, returns an array of 12 decimals, one
    for the ET Adjustment of each month. We average the `etadj` of all weather
    stations, and use that value for all months.
    """

    avg_etadj = float(sum([w.etadj for w in ws])) / len(ws)

    return [avg_etadj] * 12