In Cusco (or Cuzco), the ancient capital of the Inca Empire, located at 3,300 metres (10,800 ft) above sea level in the Andes, the climate is temperate, spring-like during the day all year round, but with cold nights in the winter period from May to August, when the minimum temperatures are near freezing (0 °C or 32 °F); on the contrary, in summer, from November to March, which is also the rainiest period, night temperatures are milder, around 7/8 °C (45/46 °F).
During the day, the temperatures are uniform throughout the year, and reach 20/22 °C (68/72 °F) when the sky is clear, also in winter, due to the strong heating caused by the mountain sun. Instead, in winter a cold mountain breeze starts to blow at sunset, and on winter nights there may be slight frosts.
During the day, the temperature never reaches 30 °C (86 °F), even though the tropical mountain sun is very strong and requires appropriate protection.
Here are the average temperatures.
Average temperatures - Cusco

Cusco	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cusco	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	7	7	6	5	3	1	1	2	5	6	6	7
Max (°C)	19	19	19	19	19	19	19	20	20	21	21	20
Min (°F)	45	45	43	41	37	34	34	36	41	43	43	45
Max (°F)	66	66	66	66	66	66	66	68	68	70	70	68

Rainfall is moderate, since it amounts to 710 millimetres (28 inches) per year, and is concentrated in the summer months, in particular it's equal to or higher than 100 mm (4 in) per month from December to March. In these months, showers occur almost daily, although they are often short-lived.
Here is the average precipitation.
Average precipitation - Cusco

Cusco	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Cusco	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	145	135	105	45	10	2	5	10	20	40	70	125	712
Prec. (in)	5.7	5.3	4.1	1.8	0.4	0.1	0.2	0.4	0.8	1.6	2.8	4.9	28
Days	18	13	11	8	3	2	2	2	7	8	12	16	102

In the winter period, from May to August, it rains very rarely. The rains begin to fall in September, although they are initially rare and brief.



The amount of sunshine in Cuzco is good in the dry season, from May to August, when blue skies prevail, it is decent in the intermediate periods, when the rains are frequent but short-lived, while it becomes quite mediocre from December to March, due to the frequent cloudiness, which can lead to showers.
Sunshine - Cusco

Cusco	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cusco	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	5	4	5	7	8	8	8	8	6	6	6	5

The best time to visit Cuzco goes from May to October, being the driest and sunniest. Since it is winter, you should be equipped for the cold at night, and be ready to uncover (but at the same time to protect yourself from the sun) during the day, when the air is mild.
In April and September there are some showers, but generally of short duration and not heavy.