Using ClickHouse local:

    time clickhouse local -q "SELECT concat('{', arrayStringConcat(groupArray(v), ', '), '}')
    FROM
    (
        SELECT concat(station, '=', min(t), '/', max(t), '/', avg(t)) AS v
        FROM file('measurements.txt', 'CSV', 'station String, t Float32')
        GROUP BY station
        ORDER BY station ASC
    )
    SETTINGS format_csv_delimiter = ';', max_threads = 8" >/dev/null

    real 0m15.201s
    user 2m16.124s
    sys 0m2.351

Most of the time is spent parsing the file