S1: Summer in Delhi is extremely hot. S2: Summer in Shimla is quite cold. The second sentence:

Both sentences talk about summer but in different locations (Delhi and Shimla) with opposite weather conditions (hot vs cold). This is not a contradiction because both can be true simultaneously - they refer to different places. The second sentence presents an opposing example to highlight the difference, which is the function of contrast. Therefore, the second sentence contrasts the assertion of the first.