Map from Google - Malawi

Malawi is an African country, located south of the equator, mostly hilly and mountainous, and has a tropical climate (or sub-tropical at high altitudes) with a hot and rainy season from mid-November to April, and a relatively cool, dry winter season from mid-May to mid-August. Before the rainy season, from September to November, the temperature rises to the point of reaching the highest levels of the year. The temperature varies with altitude: above 3,300 feet they are pleasant. However, in the far south there is a flat region, hot and humid due to the low altitude.
In much of the country, the annual precipitation is generally between 30 and 50 inches, and is generally more abundant in the north, where in particular March and April are very rainy, but also in the southern slopes of Mount Mulanje, where it even exceeds 80 inches per year. In the Mulanje Massif there's the highest peak of the country, called Sapitwa Peak, 9,800 feet high.
The capital Lilongwe is located at 3,600 feet above sea level and has mild temperatures, between 70.5 °F in January and 57 °F in July. The daytime temperatures rarely exceed 90 °F during the period from December to April, and stay around 73/77 °F from May to August. During the cooler season, from mid-May to mid-August, at night it can get cold, and even light frosts can occur. In the hottest period, ie October and November before the rains, the temperature can instead touch 95 °F. Here are the average temperatures.
Lilongwe average temperatures
Lilongwe J F M A M J J A S O N D
Min (°F) 63 63 61 55 50 45 43 45 52 57 61 63
Max (°F) 79 79 79 79 77 73 73 77 81 86 86 81

The rains fall from November to April, and amount to 33.5 inches per year, with a maximum of 8 inches in January and February, while it hardly ever rains from May to October. Here is the average precipitation.
Average precipitation Lilongwe
Lilongwe J F M A M J J A S O N D Year
Prec. (in) 8.3 8.3 5.1 1.4 0.2 0.0 0.0 0.1 0.1 0.2 2.8 6.9 33.3
Days 14 12 9 4 1 1 0 0 0 1 4 12 58

The climate in the country's second city, Blantyre, which is located in the south at 3,300 feet above sea level, is similar to that of Lilongwe.
At lower altitudes, in Karonga, at 1,650 feet above sea level near Lake Malawi, the average goes from 77 °F in January to 70 °F in July, and to 79 °F in November. Already at this altitude, the heat is muggy during the rainy season, while it can be intense in the period from September to November. Lake Malawi (or Nyasa) lies on the Rift Valley at the same altitude; along its shores there are beaches which during the afternoon are cooled by nice breezes, and from which one can enjoy the spectacular scenery of the lake surrounded by mountains.
Here are the average temperatures of Makokola, on the shores of the lake.
Makokola average temperatures
Makokola J F M A M J J A S O N D
Min (°F) 70 70 70 68 63 59 59 63 64 70 72 72
Max (°F) 84 84 86 84 82 79 79 81 86 90 90 86

Lake Malawi

Other lakes in the country are Lake Malombe, a continuation of Lake Malawi, at about the same altitude, near which the Liwonde National Park is located, and Lake Chilwa, 2,000 feet above sea level.

In the far south, in the River Shire Valley (see Chikwawa, Nsanje) the altitude drops to the plain level and, consequently, the temperature becomes higher: it regularly exceeds 90/91 °F during the day for many months, and may sometimes exceed 105 °F. Anyway, the heat becomes more bearable from May to August.
Nsanje average temperatures
Nsanje J F M A M J J A S O N D
Min (°F) 72 72 70 66 61 59 57 59 63 68 70 72
Max (°F) 90 90 90 88 84 79 79 84 90 93 95 91

The amount of sunshine in Malawi is good in the dry season, particularly in September and October, while it is not so good during the rainy season, when there are 5/6 hours of sunshine per day. The tropical rains occur mainly in the form of downpour or thunderstorm in the afternoon.
Sometimes Malawi can be affected by tropical cyclones, which penetrate inland from the Indian Ocean and affect more easily the south of the country, bringing winds and torrential rains. The Indian Ocean cyclone season runs from November 15 to May 15, but the period in which they are more likely runs from late December to mid-April.
During winter, the south of the country, but also Lake Malawi, may be affected by a cool and humid wind, the Chiperoni, which brings cloudy skies and a constant drizzle for a few days. The wind, which is channeled through the mountains, can make the lake a bit rough.

When to go

The best time to visit Malawi runs from mid-May to August, being the coolest within the dry season. It should be remembered that at higher altitudes, during this period nights can be cold with possible frosts, but you will avoid the sultry heat and the rainfall of the period from December to April, and also the blistering heat that affects the lowlands from September to November, in addition to cyclones that are possible from mid-November to mid-May. However, if you do not suffer from the heat and prefer the intense heat to the risk of a little cold at night, you can choose September and October, or the second half of August in which the temperature begins to rise.

What to pack

In winter (June-August): in Lilongwe and Blantyre, spring/autumn clothes, light for the day, sweater and jacket for the evening; for the southern plains, light clothing, a sweatshirt for the evening; for the shores of Lake Malawi, light clothing, a sweatshirt and a light jacket, a scarf for the breeze. For the mountainous areas, spring/autumn clothes for the day, sweater, warm jacket and hat for the evening, hiking shoes.

In summer (December-February): in Lilongwe and Blantyre, light clothes, sun hat, a light sweatshirt for the evening, light raincoat or umbrella; for the shores of Lake Malawi and the southern plains, loose fitting clothing, light shirts and pants of natural fibers (cotton, linen), sun hat, a light sweater for the evening, light raincoat or umbrella. For the mountainous areas, spring/autumn clothes, jacket, raincoat, sun hat, hiking shoes.