import cdsapi

# Open a new Client instance
c = cdsapi.Client()

months = ['01','02','03','04','05','06','07','08','09','10','11','12']

# Request for downloading data
for year in range(1980,2011):
  for mon in months:
    fname = 'ERA5.25d.t2m.' + str(year) + '-' + mon + '.nc'
    print(fname)
    c.retrieve(
        'reanalysis-era5-single-levels',
        {
         'product_type': 'reanalysis',
         'variable': ['2m_temperature'],
         'year': str(year),
         'month': mon,
         'day':   ['01','02','03','04','05','06','07','08','09','10','11','12',
                   '13','14','15','16','17','18','19','20','21','22','23','24',
                   '25','26','27','28','29','30','31'],
         'time':  ['00:00','01:00','02:00','03:00','04:00','05:00',
	           '06:00','07:00','08:00','09:00','10:00','11:00',
                   '12:00','13:00','14:00','15:00','16:00','17:00',
                   '18:00','19:00','20:00','21:00','22:00','23:00'],
         'format': 'netcdf',
        },
        fname)