Map from Google - Andorra

Andorra, a small mountainous country located in the Pyrenees, between France and Spain, has a temperate climate in the lower valleys, and a mountain climate at high altitudes. Precipitation is quite frequent, since Atlantic frontal systems affect the country for many months a year, while in summer, when the Azores anticyclone prevail, thunderstorms may break out in the afternoon.

The capital, Andorra la Vella, is located at 1,000 metres (3,300 feet) above sea level, in the Valira Valley, in the low part of the country; the lowest point is Sant Julia de Loria, 840 metres (2,755 feet) above sea level, in the south, near the border with Spain. Here the climate is not too cold: the average temperature in January is 2.5 °C (36.5 °F), while in July and August it's 19 °C (66 °F). Winter is cold but not freezing, although the temperature at night drops quite often a few degrees below freezing. The wind from the north has foehn-like characteristics, that is of a warm, dry wind that descends from the mountains. However, heavy snowfalls and frosts may occasionally occur.
Summer is quite warm during the day, with highs around 25 °C (77 °F), but relative humidity is not high, and nights are cool. In the afternoon, thunderstorms may occur.
Here are the average temperatures of Andorra La Vella.
Average temperatures - Andorra La V.
Andorra La V.JanFebMarAprMayJunJulAugSepOctNovDec
Andorra La V.JFMAMJJASOND
Min (°C)-1-12461012121062-1
Max (°C)671214172326242216106
Min (°F)303036394350545450433630
Max (°F)434554576373797572615043

In Andorra La Vella, precipitation amounts to 800 millimetres (32 inches) per year, and is well distributed throughout the year, although there's a relative minimum in winter and early spring, while the rainiest months are May and June, because of afternoon thunderstorms. Here is the average precipitation.
Average precipitation - Andorra La V.
Andorra La V.JanFebMarAprMayJunJulAugSepOctNovDecYear
Andorra La V.JFMAMJJASONDY
Prec. (mm)503040709085608085808060810
Prec.(in)21.21.62.83.53.32.43.13.33.13.12.431.9
Days656911977787688

In Soldeu, located 1,800 metres (5,900 feet) above sea level, the climate is much colder: the average temperature goes from -3 °C (26.5 °F) in January and February, to 12 °C (53.5 °F) in July and August. An average of 1,300 mm (51 in) of rain (or snow, from November to April) falls each year, without there being a dry season, because in summer, thunderstorms may occur in the afternoon.
Here are the average temperatures of Soldeu.
Average temperatures - Soldeu
SoldeuJanFebMarAprMayJunJulAugSepOctNovDec
SoldeuJFMAMJJASOND
Min (°C)-7-7-6-4036641-3-6
Max (°C)1135914181714941
Min (°F)191921253237434339342721
Max (°F)343437414857646357483934

The average altitude of the country is 1,900 metres (6,200 feet). In high mountains, snowfalls occur during winter. In the highest peaks, snow can linger on the ground until July. The highest point in the country is Coma Pedrosa, 2,942 metres (9,652 feet) high.

The sunshine amount in Andorra is high in summer, when sunny days are frequent, while it is just acceptable in the other months.

Andorra

When to go

The best time to visit Andorra runs from June to mid-September, being the least cold in the mountains, while in the valleys it's warm, but not too much. You should be equipped for cool temperatures at night in the valleys, and even for the cold at high altitudes, and for afternoon thunderstorms. July and August are the warmest months; July is generally less prone to thunderstorms than August.

What to pack

In winter: warm clothing, sweater, down jacket, hat and gloves.
In summer: light clothes, T-shirt, but also long pants, jacket and sweater for the evening and in the mountains; hiking shoes, sunscreen and sunglasses, raincoat or umbrella.