Toledo, where it is

In Toledo, the capital of the autonomous community of Castilla-La Mancha, located at an altitude of about 500 metres (1,600 feet), the climate is transitional Mediterranean, with some continental characteristics, and semi-arid. The daily temperature variation is often high. In winter, mild periods alternate with cold periods, in which night frosts, usually light, may occur. However, the characteristic feature of the climate of Toledo is the hot summer, with fairly frequent scorching periods, although the humidity is fortunately low.
Here are the average temperatures.
Toledo - Average temperatures
Min (°C)246811161919151163
Max (°C)121418202430353429221612
Min (°F)363943465261666659524337
Max (°F)545764687586959384726154

Precipitation is quite low, given that it totals 350 millimetres (13.8 inches) per year, and in fact the landscape is arid, especially during the summer months. The rains, however, are quite frequent in spring and autumn. In May, and more rarely in summer, some thunderstorms can break out in the afternoon, but usually from June to August it almost never rains.
Here is the average precipitation.
Toledo - Average precipitation

Winter, from December to February, is fairly mild: the average temperature in January is 7 °C (44.5 °F). Rainfall, which is brought by Atlantic depressions, is not very frequent, due to the distance from the sea, and usually it's not abundant as well. Days can be mild, particularly when the Azores anticyclone settles on the Iberian Peninsula, bringing periods of good weather also in winter, with highs around 15/18 °C (59/64 °F), but nights are usually cold, with lows around 3/5 °C (37/41 °F). Sometimes, cold waves, with snow and frost, can occur. A particularly cold episode occurred in January 2005, when the temperature dropped to -9 °C (16 °F).

Summer, from June to August or mid-September, is hot and sunny; the average July temperature is 27 °C (81 °F). The heat is usually intense during the day, since the maximum temperature easily reaches 37/38 °C (99/100 °F), with peaks of 40/42 °C (104/108 °F), although the air is dry, so it is more bearable. At night, however, the heat almost always gives a break, as the temperature decreases in a remarkable way.

Spring and autumn are mild and characterized by a variable weather, in which periods of good weather alternate with the passage of Atlantic depressions, which bring clouds and rain.

The amount of sunshine in Toledo is excellent in summer, when clear skies prevail: in July there are on average 12 hours of sunshine per day. Sunny days are possible throughout the year, but in winter the average drops to 4 hours per day in December and 5 hours in January.
Toledo - Sunshine

Toledo, Alcazar in the background

When to go

The best times to visit Toledo are spring and autumn, especially from mid-April to late May and from mid-September to mid-October. In June it can get hot during the day, especially in the second half of the month. In April it can still be a bit cold, especially in the first part of the month.
September, too, is a good month, but at the beginning it can still be hot, while during the month the first rains may occur. In October the air is often mild, however, the days get shorter, the rains are more frequent, and it can start to get a bit chilly at night, especially in the second half of the month.
Those who can stand the heat can also choose July and August, but must be prepared to stroll around the city in hot weather.
The temperature range between day and night is often high, so it is helpful to dress in layers and have available something warm: you may want a light sweatshirt for the evening even in summer.