Loch Lomond weather at a glance
Expect cool summers, mild winters and rain in every month. The figures below are climate normals, meaning averages over a 30 year period. They show the pattern, not the forecast for your week.
The reference here is the Met Office station at Paisley, a lowland site near Glasgow, for the period 1991 to 2020. It is not a measurement taken at the loch or on Ben Lomond. Hills are not the same as the lowlands, so do not read summit conditions from this table. Check a mountain forecast before you climb.
Month by month: regional reference, Paisley
Average daily highs and lows and average monthly rainfall, Met Office normals for 1991 to 2020.
| Month | Average high | Average low | Rainfall |
|---|---|---|---|
| January | 7.2 °C (45 °F) | 2.1 °C (36 °F) | 146 mm |
| February | 7.8 °C (46 °F) | 2.2 °C (36 °F) | 115 mm |
| March | 9.8 °C (50 °F) | 3.2 °C (38 °F) | 97 mm |
| April | 13.0 °C (55 °F) | 5.1 °C (41 °F) | 66 mm |
| May | 16.1 °C (61 °F) | 7.4 °C (45 °F) | 69 mm |
| June | 18.4 °C (65 °F) | 10.3 °C (51 °F) | 68 mm |
| July | 19.8 °C (68 °F) | 12.1 °C (54 °F) | 83 mm |
| August | 19.3 °C (67 °F) | 11.9 °C (53 °F) | 95 mm |
| September | 16.7 °C (62 °F) | 9.9 °C (50 °F) | 98 mm |
| October | 13.0 °C (55 °F) | 6.8 °C (44 °F) | 132 mm |
| November | 9.6 °C (49 °F) | 4.2 °C (40 °F) | 132 mm |
| December | 7.4 °C (45 °F) | 2.1 °C (36 °F) | 161 mm |
December is the wettest month in the table and April the driest. That is a reading of the numbers, not a promise of a dry April. No month is dry.
What each season means for your trip
Temperatures come from the table above. Boat and walking details come from the operators and the park.
Spring, April and May
April is the driest month in the table, with highs around 13 °C (55 °F). The daily circular cruises on the big loch start in late March. Around Conic Hill, dogs are kept out of fenced fields during lambing, usually for six weeks from mid-April to the end of May. Midges usually start in May.
Summer, June to August
July is the warmest month, with highs near 20 °C (68 °F). Boat programs are at their fullest, and the ferries from Balloch to Luss (May to September) and from Luss to Balmaha (June to September) are in service. This is also the strongest midge period.
Autumn, September and October
Highs drop from 16.7 °C (62 °F) to 13 °C (55 °F), and October rainfall rises to 132 mm. The Loch Katrine summer timetable ends on 25 October 2026. The circular cruises from Tarbet and Luss run daily to 1 November 2026.
Winter, November to March
Highs stay between 7 and 10 °C (45 to 50 °F) at Paisley, and December brings 161 mm of rain. Loch Katrine switches to 45 minute motor boat trips from 26 October 2026. The Balmaha visitor center opens only on Saturday and Sunday from November to March.
Loch Lomond tours in all seasons
Cruises and guided day trips from Glasgow and Edinburgh, with live prices and availability.
Midges and ticks
Midges are small biting flies. They usually appear from May to October, and they are strongest in high summer. They are worst in the morning and evening, in still, damp air, and they are common in wet country and woodland. No month is guaranteed midge free, so do not count on September.
Wear long sleeves and trousers, use a repellent that suits you and carry a head net if you are sensitive. After walks through grass, forest or moor, check yourself for ticks.
The Inchcailloch campsite also lists a tick risk. The island is covered in the Inchcailloch guide.
Weather, water and the hills
Mountain weather changes fast. For Ben Lomond and Conic Hill, check the forecast on the day, carry a map and compass, and wear proper hill clothing. Bring food and water. A route written for summer does not prepare you for winter conditions on the summit. In an emergency call 999, ask for the police and Mountain Rescue, and give your exact position.
The loch is cold. The water can deepen abruptly near the shore, and cold shock and hypothermia are real risks. Do not swim alone, get in slowly and stay visible. A beach is not a guarantee of clean or safe water. Local notices and warnings take priority. Clean and dry your boat, paddle gear, boots and wetsuit between waters to avoid spreading invasive species.
The camping rules also follow the season. The management zones apply from 1 March to 30 September. From 1 October 2026 to 28 February 2027 no seasonal camping permit is needed, and the Loch Chon, Loch Achray, Inchcailloch and Sallochy campsites are shown as closed. The details are in our guide on where to stay.
The best time to visit is a trade-off
There is no single best month. For boats, the longest timetables and warm days, plan on May to September, and accept midges in high summer. For the lowest rainfall in the table, look at April. For fewer visitors and quiet shores, take a mild winter day and accept shorter boat programs and plenty of rain. Shorter days also limit what you can fit in.
The A82 on the west shore has night works in October and November 2026, as described in getting there. Whatever the month, pack a waterproof jacket.
Loch Lomond weather: frequently asked questions
What is the wettest month at Loch Lomond?
At the Paisley reference station December is the wettest, with 161 mm on average. The loch and hills are not measured there, so use it as a guide only.
When is midge season?
Midges are usually active from May to October, and strongest in high summer. They bite most in the morning and evening when the air is still and damp.
What is the warmest month?
July, with an average high of 19.8 °C (68 °F) and a low of 12.1 °C (54 °F) at the Paisley reference station.
Is it safe to swim in Loch Lomond?
There is no general ban on swimming, and no general all clear either. The water is cold, can deepen abruptly near the shore and carries a risk of cold shock. Follow local notices and never swim alone.
Can I rely on a dry day for Ben Lomond?
No. Mountain weather changes quickly, and the table is from a lowland station. Check a mountain forecast on the day and turn back if conditions worsen.
Do boats run in winter?
Yes, in reduced form. From Balloch the one hour Experience Cruise runs in winter at 10:15, 11:30 and 13:00. Loch Katrine runs 45 minute motor boat trips from 26 October 2026 to 26 March 2027.