Ticks are only active in spring and summer

False. In Northern Europe ticks are active mainly between spring and autumn when temperatures are warm enough. In the study developed by Perret et al., questing tick density showed a significant increase in March for both nymphs and adults, the peak of questing nymphs being at the end of April and decreasing rapidly in June. Adult activity was prolonged until September (27).

Field surveys in Scotland, Switzerland and northern Italy have estimated a weekly average maximum daily temperature of 7–8°C for I. ricinus nymphs to emerge from their over-wintering diapause and start to quest for hosts (reviewed by (28)).

Therefore, in areas with mild winters, or in prolonged mild spells in winter, ticks may become active during the winter. Scottish ticks are better adapted to the cold than ticks from warmer climates (such as southern France or southern England): e.g. 17.2% of Scottish ticks are active when it is only 6°C (compared to 15.2% in Wales and 13% from southern England). In France ticks require a minimum temperature of 7°C to start questing (33).