We develop monthly temperature series (mean, maximum and minimum) for the Scottish mainland (SMT), the northern and northwestern Scottish Isles (SIT, Orkneys, Shetlands and Outer Hebrides) and for Northern Ireland (NIT). The series were developed from eight long station records, five over SMT, two for SIT and one for NIT. The series are reliable back to 1866 for all three regions, but extensions to 1800 and 1827 for SMT and SIT are less so, likely due to direct solar insolation effects in the summer months. All three regions show long-term statistically significant seasonal warming over both 1861-2000 and 1901-2000, except for the winter season. For the calendar year, the temperature change explained by a linear trend over 1861-2000 is 0.69°C, 0.64°C and 0.77°C for SMT, SIT and NIT respectively. Of the 51 (12 months + 4 seasons + annual = 17 × 3 regions) warmest values, 23 have occurred after 1987. Of the coldest extremes, 30 occurred between 1861 and 1899 and the last cold extreme months were in 1952.