Lanzarote, where it's located

The island of Lanzarote, the most north-eastern of the Canary Islands, has a very mild and almost desert climate, with very mild winters, and warm and sunny summers.
Along the coasts, the rains amount to less than 200 millimetres (8 inches) per year; they are due to low pressure areas that pass in the period from October to March, while in summer basically it never rains. Here is the average precipitation in Arrecife, the main city, where the airport is also located.
Arrecife - Average precipitation

Unlike other islands of the archipelago, in the interior there are no mountains high enough to cause a substantial increase in precipitation. However, at the highest point of the Famara massif, 670 metres (2,200 feet) above sea level, where the military station and the Ermita de las Nieves are found, the landscape is a bit greener, mist and fog can form quite often and there are terraced fields.
Temperatures in Lanzarote are very mild, spring-like much of the year: during the day they are between 21 °C (70 °F) in January and February, and 29 °C (84 °F) in August and September. The temperature generally tends to stay around the average, except when the wind blows from Africa, which can raise the temperature by several degrees.
Here are the average temperatures.
Arrecife - Average temperatures
Min (°C)141415161719202121191715
Max (°C)212123242526282929272422
Min (°F)575759616366687070666359
Max (°F)707073757779828484817572

The island is particularly exposed to the trade winds, which blow constantly throughout the year, from the northeast, especially in the afternoon. The waves generated by these winds are particularly appreciated by surfers.
However, as mentioned a hot and dry wind from Africa can sometimes blow, which can reduce visibility carrying dust or sand from the desert, and brings abnormally high temperatures, which usually lasts two or three days; this phenomenon has become more frequent in recent years. Lanzarote is particularly exposed to these hot winds; the highest records are 36 °C (97 °F) in April and October, and 40/43 °C (104/110 °F) from May to September.
The sun in Lanzarote shines all year round, however, in addition to the low pressure systems that may pass during the October to March period, in summer cloud banks can form on the Atlantic Ocean and pass over the island, while on the northern coast, and especially on the hill slopes exposed to the north, local clouds and mists can form. The south coast is therefore the sunniest.
Here are the average daily sunshine hours on the south-east coast.
Arrecife - Sunshine

Lanzarote is a volcanic island: in the north there is the crater of Volcán de la Corona, about 600 metres (2,000 feet) high, while in the west, in the National Park of Timanfaya, we find the Montañas del Fuego (Fire Mountains), where the landscape is lunar and characterized by craters, calderas, geysers, caves (cuevas), and soil made of volcanic rock, where tourists can make excursions by dromedary.

Lanzarote, Timanfaya National Park

To the north of Lanzarote we find the Chinijo Archipelago, made up of small islands (Montaña Clara, Alegranza and La Graciosa), and islets (Roque del Este and Roque del Oeste).

The sea is cool, because of the cold sea current, called Canary Current, which flows to the west of Morocco: the sea temperature ranges from 19 °C (66 °F) in January, to 18 °C (64 °F) in February, March and April, to 22 °C (72 °F) in the period from August to October. So basically you can try to swim also in winter, at least if you are not sensitive to cold, while in summer the sea is still cool.
Here are the average sea temperatures.
Lanzarote - Sea temperature
Temp (°C)191818181920212222222120
Temp (°F)666464646668707272727068

Beach in Lanzarote

When to go

For beach tourism and surfing, the best time to visit Lanzarote goes from May to mid-October, though having a mild climate it can be visited all year round. For the low rainfall, however, after all the island lends itself to this type of activity also in the second half of October and in November, when the sea is still relatively warm, although the first Atlantic depressions can pass, bringing some cloudiness and some rain, which can happen also in winter. On the other hand, in autumn and winter, in periods of bad weather the south wind can generate high waves, which can be appreciated by surfers.

What to pack in the suitcase

In winter: light clothes for the day, sweater and jacket for the evening, possibly a raincoat or umbrella.
In summer: summer clothes, but also a scarf for the wind, a light sweatshirt, light jacket for the evening and for windy afternoons; comfortable shoes for hiking.