Thanks a lot for your replies!!
Just to summarize:
Only on the ground, provided you have the correct QNH, the altimeter will read the correct height regardless of temperature. But as soon as you leave the ground the temperature becomes significant and my altimeter will be susceptible to temperature induced errors.
(Flying from warm to cold my true altitude will reduce)
Please correct me if I`m wrong , I don`t want to learn s.th. wrong.
bye
subsy