Pest activity in the UK is far more seasonal than most homeowners realise. The same droppings in October vs March suggest different species; the same scratching in July vs January narrows to a different animal. Use this calendar to weight your diagnosis.
Spring (March–May): nesting season
- Wasp queens emerge in late March, start small nests in April.
- Squirrels: first litter born March–April, second peak in July.
- Ants: first foraging trails appear when soil temp hits 10°C, typically mid-April.
- Pigeons: nesting peak. Legally protected during this window.
Summer (June–August): peak everything
- Wasps: nest size peaks in August; aggression spikes when queen stops feeding workers.
- Bed bugs: travel-driven spike from June onwards as holidaymakers bring them home.
- Cluster flies and fruit flies: warm, humid loft spaces.
- Ants: full nuptial flight ('flying ant day') usually mid-July.
Autumn (September–November): the indoor migration
- Rats and mice: biggest annual spike. Cooler nights drive them indoors from October.
- Cluster flies: hibernate in lofts and cavities; first sign is a sudden swarm at south-facing windows.
- Spiders: house spider mating season — the giant ones you see in September are males looking for females.
- Squirrels: second litter, plus loft incursions before winter.
Winter (December–February): the quiet months — except indoors
- Rodents: peak indoor activity. If you've got rats in the loft, this is when you'll hear them.
- Bed bugs: undisturbed by cold; infestations established in autumn often peak here.
- Cockroaches: stable year-round in heated buildings; winter call-outs cluster in flats and HMOs.
- Wildlife (foxes, badgers): mating season for foxes, peak noise in January–February.
Off-season anomalies to take seriously
Wasps active in November mean a heated cavity nest, not a normal cycle — investigate. Bed bug signs in December mean an established infestation, not a holiday import — book sooner. Mouse droppings in July mean a resident colony, not autumn migrants — treat at the entry point.