Examples

import numpy as np
import pandas as pd

df1 = pd.DataFrame([[26.3, 78.5, 'high'],
                    [32, 85.5, 'high'],
                    [21, 68.5, 'medium'],
                    [30, 90, 'medium']],
    columns=['temp_celsius', 'temp_fahrenheit', 'windspeed'],
    index=pd.date_range(start='2019-02-12',
                        end='2019-02-15', freq='D'))

df1

	temp_celsius	temp_fahrenheit	windspeed
2019-02-12	26.3	78.5	high
2019-02-13	32.0	85.5	high
2019-02-14	21.0	68.5	medium
2019-02-15	30.0	90.0	medium

df2 = pd.DataFrame([[22, 'low'],
                    [28, 'low'],
                    [33.2, 'medium']],
    columns=['temp_celsius', 'windspeed'],
    index=pd.DatetimeIndex(['2019-02-12', '2019-02-13',
                            '2019-02-15']))

df2

	temp_celsius	windspeed
2019-02-12	22.0	low
2019-02-13	28.0	low
2019-02-15	33.2	medium

df2.reindex_like(df1)

	temp_celsius	temp_fahrenheit	windspeed
2019-02-12	22.0	NaN	low
2019-02-13	28.0	NaN	low
2019-02-14	NaN	NaN	NaN
2019-02-15	33.2	NaN	medium