July is the hottest month all over Northern Hemisphere. Exceptions being the Monsoon lands and the west coast of US especially the cities of San Francisco and Los Angeles in California. In the southern Hemisphere, it is the coldest month. Let us discuss it in a little more detail.
Conditions in Northern Hemisphere
All over the Northern Hemisphere, July records the highest temperatures of whole year. In the tropics the mid-day temperatures exceed 110 F. In the temperature belt temperatures up to 95 F must be expected. Even as far North as 60 N, temperatures of over 80 F are the norm. The nigh time lows are around 75 F in the tropical belt, 65 in temperate zone and 55 F in the frigid zone.
The monsoon lands are a major exception to this general rule, however. Here June is the hottest Month, especially in South Asia where India and Pakistan are located. The cool monsoon winds hit most parts of the Indian sub-continent by the end of June and prevent further rising of the temperatures. As a result July is much cooler than if there were no monsoon.
The second exception is the Californian coast, here due the cool pacific current, the temperatures rise very slowly and reach their peak by the month of August.
Conditions in Southern Hemisphere
As the seasons are reverse in southern hemisphere, so the areas located here are passing through their mid-winter. The major difference being that the winter is much milder than the winter of the Northern Hemisphere since this hemisphere has got no vast continents like Asia and no station is located very far off from the oceans. Thus the continental effect is not that pronounced and the temperatures are quite mild. For instance, if we have a closer look at some of the famous cities located in Southern Hemisphere, we find that the winter is much less severe than that of the Northern Hemisphere. Sydney, in Australia records a high of 60 F in July (its coldest month) and a low of 40 F; which is quite equable. Even at Auckland, in New Zealand, which is located farther south, the day time temperature rarely falls below 50 F and the nights are around 35 F.
In short, July is the hottest month in the Northern Hemisphere and the coldest in the Southern Hemisphere. The temperatures recorded at a particular station is highly dependent on its distance from the nearest water body may it be a sea or an ocean.