Mosquito season UK searches usually want one neat answer, something like "May to September". That answer is roughly right for the most common house mosquito, but it hides a more interesting picture. Britain has 36 native mosquito species (UKHSA, 2024), and the UK Health Security Agency (UKHSA) publishes a separate adult activity window for many of them. Some are on the wing in March. One never stops. This article lines those windows up month by month, shows where a peer-reviewed English field study agrees and disagrees, and says plainly where no source gives month-level detail. If you want the wider question of whether Britain has mosquitoes at all, and what changed in 2026, start with our companion piece, are there mosquitoes in the UK.
Why there is no single mosquito season UK calendar
There is no official national "mosquito season" with a start and end date. What exists is a set of species profiles. UKHSA and the Centre for Climate and Health Security published a mosquito species profiles guidance page on 6 March 2025 that gives, species by species, when adults are active, how each one spends the winter, and whether it bites people (UKHSA, "Mosquitoes: species profiles"). Read together, those profiles give a season that is a stack of overlapping windows, not one block.
The second ingredient is field data. A 2024 paper in Parasites & Vectors by Seechurn and colleagues tracked Culex pipiens, the common house mosquito, at four English sites: London (trapping from 2014 to 2021), Chester Zoo, Flamingo Land in North Yorkshire and Twycross Zoo in Leicestershire (Seechurn et al., 2024, Parasites & Vectors 17:61). It is one species at a handful of sites, and the authors themselves note the sites may not be representative of the UK as a whole. We use it as a cross-check, not as a national rule.
The calendar, month by month
The table below only states what the two sources above state. Where a profile gives a range, the species is listed in every month the range covers. Nothing is filled in from general knowledge, so each row is only as complete as the profiles are.
| Month | What UKHSA's species profiles say is active or beginning |
|---|---|
| January | Culiseta annulata, which "remains active throughout the year in all life stages" |
| February | Anopheles claviger adults can appear "from February or March"; Culiseta annulata still active |
| March | Aedes detritus adults (active "from March to November"); Aedes rusticus emerging "from March"; Anopheles claviger; Culiseta annulata |
| April | Aedes punctor, Aedes caspius, Aedes cantans and Aedes annulipes adults are listed from April; Anopheles plumbeus adults "become active in April and May" |
| May | Culex pipiens and Culex torrentium adults "appear in May"; Culiseta morsitans, Culiseta litorea, Coquillettidia richiardii and Aedes dorsalis all start; Aedes geniculatus and Aedes flavescens emerge |
| June | Culex pipiens "peak in June" per the profile; Culiseta morsitans and Aedes punctor peak; Aedes cinereus and Aedes geminus join; Anopheles maculipennis group "becoming active from May to June" |
| July | Culex modestus becomes active; Coquillettidia richiardii is "most numerous during July and August" |
| August | Coquillettidia richiardii at its busiest; Anopheles plumbeus has "a second generation in August and September" |
| September | Most windows close: Aedes cantans, Aedes cinereus, Aedes dorsalis and Culex modestus end here, and the last Aedes geniculatus adults occur |
| October | Culiseta morsitans, Aedes punctor and Aedes caspius ("until late October") are still listed |
| November | Aedes detritus is the last seasonal species listed, to November; Culiseta annulata continues |
| December | Culiseta annulata only |
A few caveats are worth reading before you screenshot that table. These are the windows for particular species, not a forecast of how many mosquitoes you will meet. Many of the species listed feed mostly on birds or livestock, and the profiles say so: Culiseta morsitans, for example, "mostly feed on birds, with occasional biting reports from humans". Others, such as Aedes detritus, are described as prolific nuisance biters of people outdoors. A species being active in a month does not mean it is likely to bite you in that month.
What the English field study adds
The profile for Culex pipiens says adults appear in May and peak in June. The field study sees the same start but a later peak. Its abstract reports active adult female populations "between May and September" with peak adult abundance "between late July and early August". Nearly 90 percent of the total catch across the London sites came from week 20 to week 37, which the authors translate as mid-May to mid-September. Their statistical model found more than one mosquito per trap-night from about mid-April to early or mid-October, and describe this as the maximum effective trapping season.
Why do a species profile and a field trap disagree about June versus late July? The sources do not explain it, and we will not guess. One likely contributor is simply that a profile describes a species in general while the paper describes four specific sites in specific years, but that is an inference, not something either document says. What both agree on is the shape: nothing much before spring, a build through early summer, a high point in the middle of summer, and a taper through September.
The same paper makes the honest point about edges. Mosquitoes were "sporadically trapped throughout the year", and the authors say shorter trapping seasons at some sites limit extrapolation beyond the months they covered. So "May to September" is best read as where most of the activity sits, not as hard walls.
The extra edge: October and the autumn tail
UKHSA's own surveillance programme gives a useful official marker for when it considers activity at its highest. In its September 2026 post about the Aedes aegypti detection in East London, the agency says its egg traps "are checked biweekly between June and October, when mosquito activity is at its highest" (UKHSA, 3 September 2026). That is a June to October frame, a month or so wider than the folk version at the October end.
This fits the species table. Several species are listed into October, and one into November. It also explains why people are sometimes surprised by a bite in late autumn or very early spring: Culiseta annulata is listed as active all year because it does not enter diapause, the dormant state triggered by unfavourable conditions.
Where month-level data stops
Here is what we could not find, and have therefore not written down.
- A national start date. No source we read gives a single date for "the first mosquito of the year". The profiles give species windows and the paper gives site windows.
- Regional calendars. The profiles do not split Scotland, Wales and Northern Ireland from England, and the field study covers only four English sites. A Scottish season may differ, but no source here says how.
- Weather-adjusted forecasts. The only link between weather and timing in our sources is general: the paper's sites are English and its dates vary by year. We found no published rule such as "a warm March moves the season forward by X weeks", and we will not invent one.
- Bites per month. Neither source counts bites on people. The profiles describe feeding preferences, not monthly bite rates.
- A risk calendar. This article is about when adults are active, nothing more. For health questions the NHS is the place to read.
On the last point, the NHS describes mosquito bites as "usually small, raised and itchy" and says insect bites or stings are "not usually serious and get better in a few days", adding that you should not scratch the bite, as it could get infected (NHS, Insect bites and stings, page last reviewed 1 June 2023).
What this means in practice
If you want a rule of thumb you can defend, use the sources' own words. For the most common house mosquito, active adults sit between May and September, with the heaviest catches in the middle of that run. For the whole mosquito fauna, UKHSA's profiles stretch the window from March to November for several species, with one active all year. And for the surveillance community, June to October is the stated peak period.
For gardens, the UKHSA post's practical advice is about breeding sites: it recommends "removing standing water from gardens and outdoor spaces", including emptying buckets, containers, plant pots and blocked drains. That works at any month on the table.
If you are trying to work out whether a particular lump came from a mosquito, a midge or something else, our UK biting insects field guide compares them. And if you are curious how scent works in the evening, what smells mosquitoes hate goes through the evidence.
Misaj, a Paris based skincare brand, makes Glow Protect. On its product page, checked on 15 October 2026, the brand describes Glow Protect as a cream that "combines hydration, skin barrier support and botanical mosquito protection in a single cream designed to be worn daily", and describes the botanical side as "a natural aromatic blend that helps deter mosquitoes". It is a daily skincare cream, not a registered repellent. The full details are on the Glow Protect product page.
The short version
Is there a single date when mosquito season UK begins? No. The best-supported summary is a stack of species windows that starts in late winter for a few, builds from May, tapers through September, and tails into October and November for others, with one species active all year. Where a source gives a month we have given it with the source. Where none does, we said so.
Frequently asked questions
When does mosquito season start in the UK?
There is no single start date in the sources we read. UKHSA's species profiles list a few adults appearing from February or March, with many more starting in April and May. The common house mosquito is listed as appearing in May.
When does mosquito season end in the UK?
Most listed species finish by September. A few are listed into October, Aedes caspius until late October and Aedes detritus to November, and one species, Culiseta annulata, is listed as active throughout the year.
Which month has the most mosquitoes in the UK?
For the common house mosquito, the English field study found peak adult abundance between late July and early August, while UKHSA's profile lists a June peak. UKHSA's surveillance post describes June to October as when mosquito activity is at its highest.
Is there a mosquito season for Scotland or Wales?
The sources we fetched do not provide separate calendars for Scotland, Wales or Northern Ireland, and the field study covers four English sites only. We have not extended the dates beyond what the sources state.
Do mosquitoes disappear in winter?
Not entirely. UKHSA's profiles say some species overwinter as larvae, some as eggs and some as adults, and the field study recorded mosquitoes "sporadically trapped throughout the year".
Sources (fetched 2026-10-12; the product page re-checked 2026-10-15)
- UK Health Security Agency and Centre for Climate and Health Security, Mosquitoes: species profiles, published 6 March 2025 (adult activity windows, overwintering stage and biting notes per species). https://www.gov.uk/guidance/mosquitoes-species-profiles
- Seechurn N, Herdman MT, Hernandez-Colina A, et al., Field-based assessments of the seasonality of Culex pipiens sensu lato in England, Parasites & Vectors 2024;17:61, DOI 10.1186/s13071-024-06143-6 (activity May to September, peak late July to early August, four English sites, limitations). https://pmc.ncbi.nlm.nih.gov/articles/PMC10859028/
- UK Health Security Agency, Should I be concerned that an invasive mosquito species has been detected in East London?, 3 September 2026 (traps checked biweekly June to October "when mosquito activity is at its highest"; standing water advice). https://ukhsa.blog.gov.uk/2026/09/03/should-i-be-concerned-that-an-invasive-mosquito-species-has-been-detected-in-east-london/
- UK Health Security Agency, How we monitor invasive mosquitoes and stop them spreading in the UK, 3 December 2024 (36 native British species). https://ukhsa.blog.gov.uk/2024/12/03/how-we-monitor-invasive-mosquitoes-and-stop-them-spreading-in-the-uk/
- NHS, Insect bites and stings, last reviewed 1 June 2023. https://www.nhs.uk/conditions/insect-bites-and-stings/
- misajskin.com, Glow Protect product page, wording checked 15 October 2026. https://misajskin.com/products/glow-protect