Map from Google - Lesotho

Lesotho is a small mountainous country, enclave of South Africa, by which is entirely surrounded. The climate varies essentially with altitude: it is temperate at lower elevations, which don't go, however, below 4,600 feet, and it gets colder as you go up in altitude.
In Lesotho, the weather is often unstable, with rapid changes in wind and temperature from day to day. Winter is the driest season, while summer is the rainiest. Being in the Southern Hemisphere, it obviously has reversed seasons compared with Europe and North America.
The capital Maseru is located at 5,250 feet above sea level, but most of the country is crossed by the Drakensberg range and lies above 6,500 feet, touching 11,424 feet with Thabana Ntlenyana.
In Maseru, the climate is temperate: it's warm in summer, sometimes hot, but with cool nights, and mild in winter but with cold nights. In fact, the temperature range between night and day is generally wide. In summer, from November to March, highs hover around 81/86 °F, and lows around 54/59 °F; this is also the rainy season, due to thunderstorms in the afternoon that don't reduce too much the sunshine duration. In winter, from May to August, lows hover around freezing, while highs are around 59/64 °F.
Here are the average temperatures of Maseru.
Average temperatures - Maseru
MaseruJanFebMarAprMayJunJulAugSepOctNovDec
MaseruJFMAMJJASOND
Min (°F)595754463934343643485255
Max (°F)828175706461616673757981

Throughout the year, in Maseru 26 inches of rain fall, including more than 3.3 in from November to March, while in winter precipitation is scarce. Winter is therefore the driest season, although sometimes snow can fall. Here is the average precipitation.
Average precipitation - Maseru
MaseruJanFebMarAprMayJunJulAugSepOctNovDecYear
MaseruJFMAMJJASONDY
Prec. (in)4.33.93.52.81.20.60.40.812.43.33.528.1
Days1212118422349101188

Snowfall is more common at high altitudes, above 6,500 feet, where even rainfall is more abundant.

Lesotho

When to go

Despite the fact that it is the rainiest season, the austral summer, from November to March is the best season to visit Lesotho, because it's still sunny and at night it's less cold than the rest of the year. During the day it can get hot at lower altitudes, but the nights remain cool: even in Maseru it will be useful a sweater for the evening. In this period, however, some mountain roads may be impassable due to the rains.
We can also take into account spring and autumn, especially April, September and October, when the temperatures are mild, although there are still considerable differences between night and day; the amount of sunshine is good, rainfall is possible but not abundant. Sometimes, however, at night it can freeze even in spring and autumn, and it can snow at high altitudes.

What to pack

In winter (June to August): in Maseru, spring/autumn clothes, sweater and warm jacket for the evening; above 6,500 feet, down jacket, gloves, scarf, hat, hiking shoes.

In summer (December-February): in Maseru, light clothes for the day, sweatshirt and jacket for the evening, sun hat, light raincoat or umbrella; for the highest elevations, sweatshirt or sweater, warm jacket, hiking boots.