A continuous record since 1756 of monthly temperature data exist at the old observatory in Stockholm. The thermometer has only been moved twice since the beginning, and not more than ten meters. In ancient times the instruments were probably not of today's quality, but were of good European standard. The period 1756-1815 Is characterized by variability of observation times and less safe calculations of monthly means. From 1816 and onwards the measurements are well documented, but not until 1859 were modem formulas used. The annual temperature in Stockholm has increased since the middle of the 19th century. The linear increase between 1860 and 1990 is 1.6 °C.
A comparison with surrounding stations indicates that urban bias is responsible for about 1.0 oC of this increase. Around 1970 the urban bias seems to have reached a stable level, and since then no further urban heating occurs. The temperature record is presented in diagrams displaying the annual temperature and the four seasons separately. The quality of the series is discussed.