Why is efflorescence typically more visible in certain climates?

Efflorescence is a crystalline deposit of salts that can appear on the surfaces of masonry, and its visibility is significantly influenced by the moisture levels in the environment. Increased humidity plays a crucial role in this process. When humidity levels are high, water is more likely to penetrate porous materials like brick and concrete. As this moisture evaporates, it can dissolve soluble salts present in the masonry or soil. When the water evaporates, these salts are left behind, forming visible white efflorescence on the surface.

In contrast, other factors like UV exposure, temperature fluctuations, and rainfall may not directly contribute to the conditions necessary for efflorescence to form as prominently as increased humidity does. While these factors can influence the general deterioration of masonry materials, they do not specifically create the favorable conditions for moisture retention and evaporation that lead to the formation of efflorescence. Thus, increased humidity is the key factor that leads to greater visibility of efflorescence in certain climates.