Mengen & Yedigöller Weather by Month: When to Visit

What is the weather like in Mengen and Yedigöller, month by month?

The short answer: according to the Turkish State Meteorological Service (MGM) station in central Bolu, in July and August the average high is 27.5-28.0 °C and the average night-time low 12.5-12.7 °C; in January the average high drops to 5.4 °C and the low to -3.5 °C. The driest, sunniest stretch is July to September; the coldest, snowiest is December to February. For autumn colour come between mid-October and 15 November, for snow between December and February, and for a cool, dry summer in July or August.

Every temperature and rainfall figure in this guide comes from the official climate statistics MGM publishes for Bolu. Below you will find which station the numbers come from, a month-by-month table, and an answer to "which month should I visit Yedigöller National Park (the 'Seven Lakes')?" depending on what you want from the trip.

Which station do these numbers come from?

MGM's public statistics pages do not include a separate long-term average table for Mengen or for Yedigöller. The table below therefore belongs to the station in Bolu city centre:

• Station: Bolu (centre), MGM station no. 17070, elevation about 743 m
• Measurement period: 1929-2025
• Source: MGM, Official Climate Statistics, "General Statistical Data for Our Provinces"

According to MGM's station records, the observation station in Mengen sits at about 636 m and the station inside Yedigöller National Park at about 717 m. In other words, contrary to what many visitors assume, the lakes are not noticeably higher than Bolu city. Long-term averages for these two stations are not published on the public pages, so they are not used in the table.

Why does Yedigöller feel cooler?

Even at a similar altitude, the weather at Yedigöller differs from central Bolu. According to the Bolu Province 2024 Environmental Status Report, a Western Black Sea climate prevails in a narrow area around Yedigöller in the north of the province, and the Black Sea influence fades as you head south. In practice this means:

• Dense beech forest and the shade around the lakes usually make mornings and evenings cooler and damper.
• Because of the Black Sea influence, allow for rain in every season, summer included.
• The roads into the area cross higher ground. Coming from Ankara you pass Gerede (MGM station ~1,265 m) and Yeniçağa (~1,083 m), roughly 450-630 m higher than Mengen. In the standard atmosphere temperature falls by an average of 0.65 °C per 100 m, so in winter snow and ice start on these stretches before they reach the valley.
• Rule of thumb: treat the Bolu figures as the optimistic scenario for Yedigöller and pack one extra layer.

Temperature and rainfall by month (Bolu, MGM 1929-2025)

Month	Avg. high (°C)	Avg. low (°C)	Avg. temp (°C)	Monthly rainfall (mm)	Days with rain	Sunshine (hours/day)
January	5.4	-3.5	0.6	57.8	15.53	2.0
February	7.2	-2.5	1.9	48.3	14.38	2.9
March	11.1	-0.4	4.8	50.4	14.62	4.0
April	16.7	3.6	9.7	50.7	13.31	5.3
May	21.4	7.6	14.1	60.5	14.00	6.6
June	24.7	10.5	17.4	58.9	11.74	8.0
July	27.5	12.5	19.9	28.5	6.15	8.7
August	28.0	12.7	20.0	24.3	5.11	8.5
September	24.3	9.5	16.2	28.2	7.21	6.7
October	19.3	6.2	11.8	41.7	10.65	4.7
November	13.3	2.1	7.0	46.2	11.80	3.3
December	7.6	-1.1	2.8	59.0	14.74	2.0

Source: MGM, Bolu (centre) station. Not an exact match for Mengen or Yedigöller, but a close official reference.

How to read the table

• July, August and September are the three driest months: 24-29 mm of rain a month and 5-7 days with rain. This is the most reliable window for walking and outdoor plans.
• The wettest months are May (60.5 mm), December (59.0 mm), June (58.9 mm) and January (57.8 mm). The monthly figures add up to roughly 555 mm a year.
• Summer days and nights differ a lot: in August the average high is 28.0 °C and the average low 12.7 °C, a gap of more than 15 degrees.
• The extremes are on record too: the highest temperature MGM has measured at this station is 42.8 °C (August) and the lowest -31.5 °C (January). Even November has seen -24.8 °C.
• The last 30 years are slightly milder: in MGM's 1991-2020 climate normals the average July high is 28.2 °C and the average January low -2.4 °C. In that period the wettest month is June, with 68.9 mm.

When does it snow in Bolu?

MGM's Bolu page does not list the monthly number of snow days, but the temperature data shows the snow season clearly. The average low stays below freezing from December to March. The main snow season is therefore December to February, with November and March as transition months. According to MGM, the greatest snow depth recorded at the Bolu station is 72 cm (6 February 1950).

Month	Avg. low (Bolu)	Snow and ice outlook	Practical note
November	2.1 °C	First snow and overnight ice possible	The Bolu-Yedigöller road may close from mid-November
December	-1.1 °C	Snow season begins	Keep your dates flexible
January	-3.5 °C	Coldest month, snow most likely	Snow chains and winter tyres essential
February	-2.5 °C	Snow continues	Ice lingers in the shade
March	-0.4 °C	Night frost, late snow possible	Icy roads in the morning
April	3.6 °C	Snow rare, night frost possible	Record low -11.5 °C

When the snow arrives and how much falls varies markedly from year to year. Checking MGM's hourly and 5-day forecast for Mengen a few days before you travel tells you far more than a monthly average. Yedigöller does not have its own entry among MGM's province and district forecast pages, so the most practical approach is to look at the Bolu and Mengen forecasts together.

Which month should I visit Yedigöller?

There is no single "best month"; the right month depends on what you want to see.

Goal	Best time	Weather (Bolu, MGM)	Watch out for
Autumn colour	Mid-October to 15 November	October 19.3 / 6.2 °C, November 13.3 / 2.1 °C	Busy weekends, frequent morning fog
Snow scenery	December to February	January avg. low -3.5 °C	The park road from the Bolu side may close
Cool summer	July and August	Days 27.5-28.0 °C, nights 12.5-12.7 °C	A fleece for the evenings is a must
Quiet weekend	September, first week of October, late November	September 24.3 / 9.5 °C, 7.21 days with rain	You miss the colour peak
Green spring and hiking	May and June	May 21.4 / 7.6 °C	Among the wettest months of the year
Mist and reflection photos	October and November mornings	October avg. low 6.2 °C	Early start, flask of tea

Autumn: mid-October to 15 November for colour

The colour peak at Yedigöller usually falls between the second half of October and 15 November. Days are mild (an average October high of 19.3 °C) and mornings chilly (an average low of 6.2 °C). For a week-by-week calendar see our Yedigöller autumn foliage calendar 2026. Autumn weekends are the busiest time in the area; if you can, come midweek.

Winter: December to February for snow

Under snow, Yedigöller swaps crowds for silence. But your plan depends entirely on the roads: the Bolu-Yedigöller route can close because of snow and ice, and in that period the Yeniçağa-Mengen-Yazıcık route is used instead. For details read how to reach Yedigöller in winter via the Mengen road.

Summer: July and August for cool, dry weather

These are the sunniest (8.5-8.7 hours a day on average) and driest months of the year. Our guide to a cool summer break in Bolu will help you plan.

Quiet times: September and late November

In the Bolu data September is one of the driest months of the year (28.2 mm), and with daytime highs of 24.3 °C it is ideal for walking; the forest is still mostly green. By late November the colour is over, fog and the texture of the bare forest take over, and visitor numbers drop.

Is Bolu cool in summer?

Yes, but you feel the coolness mostly at night. Comparing MGM's long-term data, the daytime difference is a few degrees while the night-time difference is much larger:

City (MGM, long-term)	July high	July low	August high	August low
Bolu (1929-2025)	27.5 °C	12.5 °C	28.0 °C	12.7 °C
Istanbul (1950-2025)	29.7 °C	20.5 °C	29.7 °C	20.8 °C
Ankara (1927-2025)	30.4 °C	15.9 °C	30.6 °C	16.1 °C

On August nights Bolu is on average about 8 degrees cooler than Istanbul and 3.4 degrees cooler than Ankara. During the day it is only 1.7 degrees cooler than Istanbul, so the midday sun is still warm. Forest shade and the lakeshore widen the gap during the day as well.

What should I wear and pack for each season?

Season	Temperature range (Bolu avg.)	Must-haves	Often forgotten
Winter (December-February)	-3.5 to 7.6 °C	Waterproof coat, hat, gloves, thermal base layer, non-slip boots	Spare socks, a blanket for the car
Spring (March-May)	-0.4 to 21.4 °C	Layers, rain jacket, waterproof shoes	A fleece for the evening
Summer (June-August)	10.5 to 28.0 °C	Sun hat, sunscreen, light walking shoes	A cardigan or fleece for the night, a rain jacket in June
Autumn (September-November)	2.1 to 24.3 °C	Three thin layers, non-slip soles, a flask	Gloves (November), a spare battery

For a detailed autumn list see the Yedigöller autumn packing list.

How should I drive the Mengen and Yedigöller roads in winter?

On a winter journey what matters is not the average but that day's road conditions. According to the snow and ice note from Türkiye's General Directorate of Highways (KGM), roads may be closed to traffic temporarily when snow and blizzards cut visibility, and it can take time for them to return to normal.

Before you set off, follow this order:

1. Weather forecast: check MGM's forecasts for Bolu and Mengen; look not only at temperature but at precipitation and wind too.
2. State roads: the KGM road information line 0312 449 91 99 and the Closed Highways Query on Türkiye's e-Government portal (e-Devlet) show closed roads on the KGM network, the reason for each closure and the section affected.
3. Park road: for the forest road up to Yedigöller, call the National Parks Bolu Branch Directorate: 0374 215 52 81.
4. Vehicle kit: KGM recommends always carrying snow chains, a tow rope and wheel chocks in winter. Practise fitting the chains at home.
5. Winter tyres: compulsory for commercial passenger and goods vehicles from 1 December to 1 April; for private cars there is no legal requirement, but do not drive these mountain roads without winter tyres.
6. Driving: do not overtake snowploughs; the road ahead of them may not have been cleared. According to KGM, salt spread on the road does not melt ice below -9 °C, so on very cold mornings even a salted road can be slippery.
7. Do not push on through a closed road: follow the officials' directions and take the alternative route.

Whatever the season: staying at Nesilce

Nesilce Tatil Köyü is in Hacıahmetler, Mengen (Bolu), 48 km from Yedigöller National Park, and is open all year. Being on the Yeniçağa-Mengen-Yazıcık winter route makes it easier to stay in the area even when the park road from the Bolu side is closed. Central Bolu is about 50 minutes away (55 km), Istanbul about 3 hours and Ankara about 2.5 hours.

• Options: standard bungalows for 2-3 guests, duplex bungalows for 4-6 guests and standard hotel rooms for 2
• Included: a Turkish village breakfast, free parking, free Wi-Fi
• Pets: welcome with prior notice
• Good to know: there is no pool and no jacuzzi

You can compare the room types on our bungalows in Bolu page.

How to book

1. Choose your dates by goal: mid-October to 15 November for colour, December to February for snow, July and August for a cool summer.
2. Ask early for autumn weekends; midweek dates are more flexible.
3. Check availability by phone or WhatsApp via our contact page, or book through the official listings: Airbnb · Hotels.com.
4. For winter dates, confirm the road conditions the day before you arrive.

Sources

• MGM, Official Climate Statistics: Bolu (1929-2025)
• MGM, Provincial Climate Normals: Bolu (1991-2020)
• MGM, Official Climate Statistics: Istanbul and Ankara
• MGM, Bolu-Mengen weather forecast
• KGM, Snow and Ice Operations (Kar ve Buzla Mücadele Çalışması)
• e-Devlet, Closed Highways Query (Karayolları Trafiğe Kapalı Yol Sorgulama)
• Ministry of Environment, Urbanisation and Climate Change, Bolu Province 2024 Environmental Status Report
• Dünya newspaper, "Compulsory winter tyre rule starts nationwide today" (1 December 2023, in Turkish)

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To plan which month suits you and check current availability, call us on +90 507 922 11 18 or send a WhatsApp message.