Diurnal temperature variation is the significant difference between the highest temperature during the day and the lowest at night, commonly observed in arid and semi-arid regions. This phenomenon occurs due to the lack of humidity and cloud cover in these areas. During the day, the sun's rays heat the ground directly, leading to high temperatures. At night, the absence of clouds results in rapid heat loss from the ground to the atmosphere, causing temperatures to drop significantly. This extreme variation can stress both flora and fauna, necessitating specific adaptations. Plants in these regions, such as cacti, have adapted by storing water and having minimal leaf surface area to reduce water loss. Animals have adapted through nocturnal lifestyles, burrowing, and physiological adaptations to conserve water. For humans, living in such climates demands robust infrastructure and lifestyle adjustments. Buildings are often designed with materials and structures that mitigate daytime heat and retain warmth at night. Traditional practices, such as siesta during peak heat hours, are also common adaptations. Understanding and adapting to diurnal temperature variation is crucial for survival in arid and semi-arid climates, influencing ecological, social, and economic aspects of life in these regions.

The rain shadow effect is a climatic phenomenon that significantly contributes to aridity in certain regions. It occurs on the leeward side (downwind) of mountain ranges. As moist air ascends the windward side of a mountain, it cools and condenses, forming clouds and precipitating most of its moisture. When the air descends on the leeward side, it warms up, reducing its relative humidity and creating drier conditions. This process results in one side of the mountain receiving most of the rain, while the other side, the rain shadow area, remains dry. For example, the Sierra Nevada mountain range in North America creates a rain shadow effect, leading to the arid conditions in the Great Basin region. This effect is a crucial factor in forming arid and semi-arid climates, particularly in regions where mountain ranges are aligned perpendicular to prevailing wind directions.

Vegetation in arid and semi-arid climates has evolved remarkable adaptations to survive the harsh conditions of extreme heat, intense sunlight, and scarce water availability. Plant life in these regions exhibits several survival strategies. One common adaptation is the development of deep root systems, enabling plants to access water from deep underground sources. Another adaptation is the reduction of leaf size, with some plants having small leaves or spines, which minimise water loss through transpiration. Some plants have succulent characteristics, storing water in their leaves, stems, or roots, allowing them to survive prolonged dry periods. Additionally, many plants have a waxy coating on their leaves or stems to reduce water loss and reflect intense sunlight. Certain species also show rapid life cycles, germinating, flowering, and seeding in the brief periods when moisture is available. These adaptive strategies enable plants to not only survive but also thrive in arid and semi-arid environments, contributing to the unique biodiversity of these regions.

Ocean currents significantly impact the climate of hot arid and semi-arid regions. Cold ocean currents, running along the western coasts of continents, play a key role. As these currents move from higher latitudes towards the equator, they cool the adjacent land air. This cooling effect increases the air's density, leading to the formation of high-pressure areas. The high pressure inhibits cloud formation and, consequently, precipitation. An example of this is the Benguela Current along the coast of Namibia, which contributes to the aridity of the Namib Desert. Additionally, the cold current cools the air above the water, making it sink and creating a stable, dry atmospheric condition. This stability further prevents the formation of rain-bearing clouds, reinforcing the aridity of coastal regions adjacent to these currents. Hence, ocean currents are instrumental in maintaining the dryness of adjacent coastal arid and semi-arid regions.

Wind systems play a significant role in affecting moisture distribution in hot arid and semi-arid regions. The trade winds and westerlies, in particular, influence these climates. In the subtropical regions, where these climates are predominantly found, the trade winds originating from the high-pressure belts move towards the equator. These winds are typically dry, as they descend from higher altitudes, losing their moisture content. This descending, dry air contributes to the aridity of the regions it passes over. Similarly, the westerlies, blowing from west to east in the mid-latitudes, often carry moisture away from these regions, further reducing the chances of precipitation. The interaction of these wind systems with geographical features like mountains can enhance the dryness through the rain shadow effect, as seen in areas like the Patagonian Desert in South America. Thus, wind patterns are a critical factor in shaping the arid and semi-arid climates by influencing the distribution and availability of moisture.