date        time       air_temperature  dewpoint_temperature   wind_speed  wind_direction cloud_cover
01.01.2001  00:00         10.0            -1.0                1.5        2.0            10.0
01.02.2001  12:00:00.0         10.0            -1.0                1.5        2.0            10.0
31.12.2001  00:00:00.0         10.0            -1.0                1.5        2.0            10.0