In Lebanon the climate is Mediterranean on the coast, with mild and rainy winters and hot and sunny summers, while in inland areas it becomes more continental, with relatively cold winters and torrid summers.
The rains occur only between October and April, and sometimes in May, and are more abundant in winter: therefore they follow the Mediterranean pattern. This pattern is followed even in inland areas, although the rainfall become more scarce in the eastern part of the country.
From June to September it almost never rains, and the sun shines everywhere.

On the Lebanese coast, where the capital Beirut and other cities such as Tripoli and Tyre are found, the climate is typically Mediterranean. Winters are mild, in fact the average temperature in January is about 14 °C (57 °F), but they are also rainy, with particularly abundant rains in December and January; summers are constantly sunny, hot and muggy but tempered by sea breezes. Average maximum temperatures in summer are around 30 °C (86 °F) in July and August.
Here are the average temperatures of Beirut.
Beirut - Average temperatures
Min (°C)111113151822242524211613
Max (°C)171820232528303130282319
Min (°F)525255596472757775706155
Max (°F)636468737782868886827366

In the average year, in Beirut, 825 mm (32.5 in) of rain fall, with heavy rainfall in winter. Here is the average precipitation.
Beirut - Average precipitation

In Beirut, and in general in Lebanon, the sun shines regularly in summer, while in winter there is an alternation of cloudy and sunny days.
Beirut - Sunshine

The sea is warm enough for swimming from June to October, as we can see in the following table.
Beirut - Sea temperature
Temp (°C)181717182124262727252220
Temp (°F)646363647075798181777268

On the range of Mount Lebanon, the winter rains are even more abundant than on the coast, at least on the western slope, being exposed to maritime currents, which are forced to rise and condense in clouds. With increasing altitude, the temperature naturally decreases, so that in winter these mountains experience heavy snowfalls, and in the worst winters a large amount of snow can fall. Mount Lebanon is the highest chain in the country, culminating in Qurnat as Sawda', 3,087 metres (10,128 feet) high. Snow covers the mountains above 2,000 meters (6,500 feet) for almost 4 months a year, and above 2,500 meters (8,200 feet) for about 6 months a year.
At 2,000 metres (6,500 feet) above sea level, the average temperature in January is about 0 °C (32 °F), as we can see from the data of the Cedars Ski Resort, located in the north of the country, east of Tripoli.
Ariz - Average temperatures
Min (°C)-2-3-11610151311630
Max (°C)2259152022221915126
Min (°F)282730344350595552433732
Max (°F)363641485968727266595443

In the Bekaa Valley, at an altitude ranging between 900 to 1,200 metres (2,900 and 3,900 feet), in winter the climate becomes colder than on the coast, also due to the altitude, and still quite hot in summer, despite the altitude.
Here are the average temperatures in Baalbek, at 1,100 metres (3,600 feet) above sea level.
Baalbek - Average temperatures
Min (°C)-1026912141412941
Max (°C)8101318222729292722159
Min (°F)303236434854575754483934
Max (°F)465055647281848481725948

Given the relatively low temperatures, during cold spells that may affect Lebanon and the Middle East in winter, abundant snowfalls may occur, followed by frosts. The average January temperature in Baalbek is 3 °C (38 °F), while at 900/1,000 metres (2,900/3,300 feet), it rises to 5/6 °C (41/43 °F).

Snow on the temple of Bacchus in Baalbek

In summer, days are hot, around 29 °C (84 °F) in Baalbek, and a few degrees above in the cities located at a lower altitude, around 900 metres (3,000 feet), and sometimes they can be torrid, but nights are still quite cool, because of the altitude.
Precipitation, still concentrated in the winter months, is a bit less abundant than on the coast or the western slope, but it is nonetheless significant, around 100/150 mm (4/6 in) from December to February. Here is average precipitation in Baalbek.
Baalbek - Average precipitation

In the eastern part of the country, we find the Anti-Lebanon mountain range, which is cold in winter but more arid, especially in the northern part, while in the south, near Mount Hermon, during winter heavy snowfalls can occur.
In spring, and more rarely in autumn, Lebanon can be affected by a strong wind coming from the desert, called Khamsin, which can cause sudden increases in temperature and bring sandstorms.

When to go

The best times to visit Lebanon are spring and autumn: the coastal cities, including Beirut, and the Bekaa Valley as well, can be visited in April-May and September-October, bearing in mind that in the Bekaa Valley, in April and October nights are very cool or even cold.
For a beach holiday, you can go from mid-May to mid-October, although as we have seen the sea reaches 24 °C (75 °F) only in June.

What to pack

In winter: for Beirut and the coast, spring/autumn clothes, sweater and jacket, raincoat or umbrella. For the Bekaa Valley: warm clothes, jacket, hat, umbrella or raincoat, hiking shoes; for the highest mountain, mountain clothing.
In summer: for Beirut and the coast, light clothing, a light sweatshirt for the evening. For the Bekaa Valley, light clothes, sun hat, sweatshirt or sweater for the evening, scarf, hiking shoes, sleeping bag for overnight stays outdoors. For the highest mountain, a jacket and a sweatshirt.