May and September: long enough daylight, the high ground normally clear of snow, and — critically for this trail — midges either not yet active (May) or fading fast (September). June is a close third for daylight but midges are already a factor by then.
This trail runs a real climate gradient along its length: Milngavie and Loch Lomond sit in the milder, drier Central Belt, while the Highland interior around Rannoch and Glencoe is colder, far wetter (roughly 1,700 mm a year against roughly 1,400 mm in the south) and holds snow on the high points well into spring in a cold year. Midges are the single most decisive planning fact for most walkers — present from around early June to early September, worst in still, humid evenings on the sheltered, wooded Loch Lomond shoreline — and are exactly why May and September are rated above the warmer peak-summer months. Winter is a separate proposition again: the low-level southern half is a reasonable if muddy walk most of the year, but the Devil's Staircase and the Rannoch Moor crossing become genuine winter hillwalking (snow, ice, short daylight) from around November to March.
Month-by-month guide
January
Poor
The official trail guidance itself says this section of the year should only be attempted by walkers with winter hillwalking experience: snow on the high ground (Devil's Staircase, the approach to Rannoch Moor) can make navigation and footing genuinely serious, on top of the shortest daylight of the year.
6-7°C high · -0-2°C low · ~7.6 hrs (sunrise ~08:40, sunset ~16:15)Watch for: Genuine winter-hillwalking conditions on the Devil's Staircase and Rannoch Moor crossing — ice axe/crampon skills and navigation in poor visibility are the relevant concern, not just cold.
February
Poor
Daylight is improving but the high ground still carries winter conditions, and this remains within the period the trail's own guidance flags as needing winter skills.
6-7°C high · -0-2°C low · ~9.6 hrs (sunrise ~07:55, sunset ~17:35)Watch for: Same winter-hillwalking concern on the Devil's Staircase and Rannoch Moor as January.
March
Mixed
Daylight lengthens quickly, but this is unpredictable transition weather: a late-winter storm can still put snow back on the high ground even after a mild spell.
8-9°C high · 1-3°C low · ~12.0 hrs (sunrise ~06:45, sunset ~18:45, clocks change late in the month)Watch for: Don't assume winter is over on the high sections just because it feels like spring at low level.
April
Good
Midges are not yet active, days are long enough for full stages, and the route is largely clear of snow in a normal year, though a late cold snap can still catch the Devil's Staircase.
11-12°C high · 2-4°C low · ~14.6 hrs (BST from late March; sunrise ~06:15, sunset ~20:35)Watch for: Nights are still cold; snow cannot be entirely ruled out on the Devil's Staircase this early.
May
Excellent
The trail's own sweet spot: long daylight, the high ground normally clear of snow, and midges still largely dormant. This is widely regarded as the best month, which is exactly why it is also the hardest to book.
14-15°C high · 5-6°C low · ~16.8 hrs (sunrise ~05:15, sunset ~21:35)Watch for: Ticks becoming active in bracken and long grass from this point.
June
Good
The longest days of the year and generally reliable weather, but midges start biting from early in the month and get progressively worse, especially in still, humid weather on the Loch Lomond section.
16-18°C high · 8-9°C low · ~17.8 hrs (sunrise ~04:30, sunset ~22:10, longest days of the year)Watch for: Midges become a real factor from early June onward, worst at dawn and dusk in still, damp conditions on the wooded, sheltered Loch Lomond shoreline; a breeze clears them almost completely.
July
Mixed
Warm and long-dayed, but this is peak midge season on top of peak crowds and the tightest accommodation — the combination is what pushes many experienced walkers to choose May or September instead.
17-19°C high · 10-11°C low · ~17.4 hrs (sunrise ~04:50, sunset ~21:55)Watch for: Midges at their worst on still, humid evenings, particularly in the sheltered woods along Loch Lomond; a repellent and headnet make a real difference. Ticks also active.
August
Mixed
Still midge season and still busy with summer holiday traffic, though days are already noticeably shorter than June/July.
17-19°C high · 9-11°C low · ~15.3 hrs (sunrise ~05:35, sunset ~20:55)Watch for: Midges remain a real nuisance, especially on Loch Lomond in still weather.
September
Excellent
Midges are fading fast, the trail is much quieter than summer, heather colour is at its best on the moorland, and the weather is often more settled than August. Many rate this alongside May as the best time to walk.
15-17°C high · 7-9°C low · ~12.6 hrs (sunrise ~06:35, sunset ~19:15, equinox late in the month)Watch for: Midges taper off through the month but a warm, still spell early on can still bring a few days of them.
October
Good
Midges are essentially gone and the birch and rowan colour is excellent, but daylight and weather both deteriorate through the month, especially after the clocks change.
11-13°C high · 5-6°C low · ~10.1 hrs (BST for most of the month; clocks change late in the month)Watch for: The clock change cuts a further hour of usable light; start treating the Devil's Staircase and Rannoch Moor crossing as a genuine winter-hillwalking proposition again if conditions turn.
November
Mixed
Short days and heavy rain, with snow now a real possibility on the high ground, but the low-level southern half (Milngavie to Loch Lomond) stays a reasonable, quiet winter walk on its own.
8-9°C high · 2-4°C low · ~8.0 hrs (sunrise ~08:05, sunset ~16:05)Watch for: Official guidance is that November-March on the high ground needs winter hillwalking experience and kit; treat the Devil's Staircase and Rannoch Moor accordingly.
December
Poor
The shortest days and wettest, stormiest month of the year, with the high ground now firmly a winter-hillwalking proposition rather than a summer trail.
6-7°C high · -0-1°C low · ~6.7 hrs (sunrise ~08:45, sunset ~15:35, shortest days of the year)Watch for: Under 7 hours of daylight is the binding constraint on any stage; the Devil's Staircase and Rannoch Moor crossing need winter skills and kit in a way the rest of the route does not.
Sources and research notes · 8 sources
metoffice.gov.ukGlasgow/Bishopton station (near Milngavie, southern/Central Belt end), 1991-2020 averages: temp high c, temp low c, rain mm, rain days for the milder/drier end of the monthly ranges, all 12 months.Checked 28 Jul 2026
metoffice.gov.ukTulloch Bridge station (Highland interior, used as the nearest representative upland analogue for the Rannoch Moor/Glencoe character of the route — no official station sits directly on Rannoch Moor or the Devil's Staircase), 1991-2020 averages: temp high c, temp low c, rain mm, rain days for the colder/much wetter end of the monthly ranges, all 12 months, and the winter sub-zero overnight lows.Checked 28 Jul 2026
api.sunrise-sunset.orgSunrise/sunset/day-length for the central section (Tyndrum latitude), January anchor, used with the June anchor to derive daylight hours for all 12 months via standard solar-geometry interpolation.Checked 28 Jul 2026
api.sunrise-sunset.orgSunrise/sunset/day-length June anchor, used to derive daylight hours for all 12 months and cross-check the December/June extremes.Checked 28 Jul 2026
westhighlandway.orgOfficial trail guidance that November-March on the high ground should only be attempted by experienced walkers with winter skills and navigation/ice-axe/crampon kit; Loch Lomond & Trossachs National Park camping byelaws (March-September) confirmation; general midge and accommodation-booking advice. Used across winter ratings/watch for and avoid months.Checked 28 Jul 2026
hillwalktours.comMidge season timing (biting females from early June, worst June-August, fading by September), behaviour (still/humid/dawn-dusk worse, wind clears them), and recommendation of May/September as midge-light. Used in June-September rating and watch for fields.Checked 28 Jul 2026
lochlomond-trossachs.orgLoch Lomond & Trossachs National Park Camping Management Byelaws: permit required 1 March-30 September in specific lochside zones (under 4% of the park), unrestricted camping under the Scottish Outdoor Access Code outside those zones or that period. Used in March/October services fields and booking pressure.Checked 28 Jul 2026
goingthewholehogg.comConfirms Rowardennan, Inveroran and Kingshouse as the accommodation pinch points with very limited beds that sell out fastest; used in crowds/booking pressure fields.Checked 28 Jul 2026