Hot arid environments, commonly referred to as deserts, typically experience temperatures ranging from $20^\circ C$ to $49^\circ C$.

These regions are characterized by significant temperature fluctuations. During the day, especially in the height of summer, temperatures can soar to an average between $38^\circ C$ and $49^\circ C$. This extreme heating occurs due to the intense solar radiation these areas receive, coupled with minimal cloud cover that would otherwise diffuse the sunlight. Furthermore, the scarcity of vegetation contributes to elevated daytime temperatures, as there is little shade available and negligible evapotranspiration to cool the air.

Conversely, nighttime temperatures can drop dramatically, often plummeting to around $20^\circ C$ or even lower. The clear skies that facilitate intense solar heating during the day also allow for rapid heat loss after sunset. The dry air, combined with the absence of vegetation, means that there is insufficient capacity to retain heat, leading to significant cooling once the sun goes down.

It is essential to recognize that these temperatures represent averages, and actual readings can vary based on specific location and seasonal changes. For instance, the Sahara Desert has recorded summer temperatures reaching as high as $58^\circ C$, while winter temperatures can dip below freezing. In contrast, the Atacama Desert in Chile, known as one of the driest places on Earth, exhibits a more moderate temperature range due to its coastal proximity, with average temperatures fluctuating between $0^\circ C$ and $25^\circ C$.

In summary, hot arid environments experience extreme temperature variations, with daytime temperatures frequently exceeding $38^\circ C$ and nighttime temperatures dropping to around $20^\circ C$. These fluctuations result primarily from the lack of cloud cover and vegetation, which facilitate intense solar heating during the day and rapid heat loss at night.