Ngorongoro, where it is

In the Ngorongoro Conservation Area, south-east of the Serengeti, the climate is subtropical, being influenced by the altitude: the temperature is mild during the day, and cool (or even a little cold) at night, and is higher from September to April and lower from May to August, although the difference throughout the year is not remarkable. The crater's rim is located at about 2,300 metres (7,500 ft) above sea level: in the Ngorongoro Crater Lodge the average daily temperature is about 16 °C (61 °F) from October to April, while it drops to 13/14 °C (55/57 °F) from June to August; at night it's a bit cold, and drops below 10 °C (50 °F) from May to October, but sometimes also in the rest of the year.
Here are the average temperatures of the Crater Lodge, located, as mentioned, at 2,300 metres (7,500 ft) above sea level.
Ngorongoro - Average temperatures
Min (°C)1010101110888891010
Max (°C)232322212019192021222222
Min (°F)505050525046464646485050
Max (°F)737372706866666870727272

Inside the crater the altitude is a bit lower, around 1,700 metres (5,600 ft), and so the temperature is 3/4 degrees Celsius higher; here there is a lake, called Magadi or Makat (not to be confused with Lake Magadi in Kenya), inhabited by thousands of pink flamingos, while to the north-east there is a smaller lake, Embagai. Instead, to the west and east of the crater, there are areas where the altitude even exceeds 3,000 metres (9,800 ft) above sea level: they are colder and wetter, often covered with clouds and occupied by forests.
Precipitation around the crater amounts to about 1,000 millimetres (40 inches) per year, and is higher than in surrounding areas, which as mentioned are located at lower altitudes and are more arid as well as warmer. There is a dry season from June to September, which, therefore, corresponds to the coolest period, and a rainy season from October to May. Within the latter season we can identify two rainy periods: the "short rains" from October to December, and the "long rains" from March to May, with April as the rainiest month of the year. However, the rains are abundant enough also in January and February, around 90/110 mm (3.5/4 in) per month. On the contrary, in the dry period, from June to September or October (until the short rains begin) there is little rain.
Here is the average precipitation, still at the Crater Lodge.
Ngorongoro - Average precipitation

The amount of sunshine in the Ngorongoro Conservation Area is good, but not great, since in addition to the rains, which occur in the form of showers and thunderstorms, a bit of cloudiness can form also in the dry season. However the sun is very strong (we are just south of the Equator, and in addition at high elevations), so it requires appropriate protection.
Ngorongoro - Sunshine

Ngorongoro Wildlife Lodge

The Ngorongoro Crater, a UNESCO World Heritage Site, is a large volcanic caldera with a diameter of about 16 kilometres (10 miles), and is famous because it boasts a rich fauna of the environment of the savannah: hippos, black rhinos, giraffes, elephants, crocodiles, antelopes, gazelles, wild dogs, hyenas, leopards, lions etc.
Wildebeests and zebras, in the context of the "Great Migration" of the plains of Serengeti and Masai Mara, in January and February arrive in the area, and spread between the northern slope of the crater and the Olduvai Gorge, where they come to breed.

Ngorongoro map

The Olduvai Gorge, the "cradle of mankind", is located at about 1,400 metres (4,600 feet) above sea level, north-west of the Ngorongoro area; beyond the gorge there is the Serengeti. About 40 kilometres (25 miles) to the south-east, we find Lake Manyara, 950 metres (3,100 ft) above sea level; to the south-west there is lake Eyasi, about 1,000 metres (3,300 feet) above sea level. Further to the north-east, about 90 km (55 mi), near the border with Kenya, we find Lake Natron, 600 metres (2,000 feet), in a branch of the Rift Valley. The lower you go in altitude, the warmer the weather is, and from October to March it can be hot during the day.

Zebras and flamingos in the Ngorongoro area

When to go

The best time to visit the Ngorongoro Conservation Area goes from June to September, being the dry season. You must be equipped for the cold at night, and be ready to remove the outer layer during the day. In September, the temperature begins to rise a bit, and at lower altitudes during the day it can get hot; in October the temperature rises further, and at the beginning it is still dry, but in the course of the month the short rains begin.
To spot the herds of wildebeest and zebras that make the "great migration", you can choose January and February, when the animals arrive in this area. In this period the temperature is high enough, and the days are hot at lower altitudes; the afternoon showers are relatively frequent, but less than in the two real rainy seasons (long and short rains).