Map from Google - Ngorongoro

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

Inside the crater the altitude is a bit lower, around 5,600 feet, and therefore the temperature is a few degrees 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, west and east of the crater, there are areas where the altitude even exceeds 10,000 feet above sea level: they are colder and wetter, often covered by clouds and occupied by forests.
Precipitation around the crater amounts to about 40 inches per year, and is higher than the 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, thus corresponding to the coolest period, and a rainy season from October to May. Within the latter 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, even in January and February the rains are abundant enough, around 3.5/4.3 inches per month. In the dry period, however, 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.
Average precipitation - Ngorongoro
Prec. (in)

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 even 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 wildlife lodge

The Ngorongoro crater, UNESCO World Heritage Site, is a large volcanic caldera of about 10 miles in diameter, and is famous because it is home to 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 4,600 feet above sea level, north-west of the Ngorongoro area; beyond the gorge there is the Serengeti. About 25 miles to the south-east, we find Lake Manyara, 3,100 feet above sea level; to the south-west there is lake Eyasi, about 3,300 feet above sea level. Further to the north-east, about 55 miles, near the border with Kenya, we find Lake Natron, 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).