**2. Local climate**

The climate of the Caribbean is characterized as subtropical with relatively dry winters and wet summers [4]. The dominant large-scale atmospheric influence on the climate is the North Atlantic subtropical high (NAH). The average temperature at the San Juan, Puerto Rico, station last year was 80.74°F. **Figure 1** shows the annual temperature between the years 2000 and 2018 for the months of January and September [5]. On the other hand, the amount of rainfall varies considerably throughout the study area. Most of the rainfall occurs during the month of August with 7.15 inches on average for the last 20 years. The month of February is considered the dry season with 2.32 inches.

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**Figure 2.**

*Study locations, Puerto Rico.*

*Urban Heat Island Effects in Tropical Climate DOI: http://dx.doi.org/10.5772/intechopen.91253*

been selected, which cover the island (see **Figure 2**).

16,600 inhabitants, and in 2019 it has 46,000 residents [6].

difference between temperature increases was around 3.46°F.

The study UHI is based on the premise that significantly warmer surface temperatures exist in urban settings as opposed to their surrounding rural areas. To make sure that this premise is correct for the Puerto Rico case, seven locations have

The research began with the use of historical temperature data taken from the southeast regional climate center webpage. The website has the advantage of having historical data such as temperature and precipitation of at least 50 years. For this research, the temperature was the parameter for defining the problem. Data with more than five decades were used to study the changes in temperature between the

The city of San Juan, Puerto Rico (18.44, −66, geographic coordinates in decimal degrees latitude and longitude), is designated as an urban area, and it is the capital city of Puerto Rico. The number of residents in the city is declining from 428,800 in 1957 to 321,000 in 2019. The city designated as a rural area is Gurabo, Puerto Rico (18.25, −66, geographic coordinates in decimal degrees latitude and longitude), located at 20 km from San Juan, Puerto Rico. In 1957 it was estimated that it had

**Figure 3** shows the difference in temperature between urban and rural areas. The data was taken from 1957 to 1967 at each station and displays a difference in temperature on average of 2.62°F. Furthermore, the same comparative analysis was carried out for the years between 2008 and 2018 (see **Figure 4**). For this case, the

Stations located in San Juan, Puerto Rico, and Gurabo, Puerto Rico, show that both period 1957–1967 and period 2008–2018 temperatures are on the rise in heavily urbanized areas where there is a conversion of natural vegetation to urban dwellings. A NASA study found that in the summer months, the temperature in New York was on average 4°C higher than in the surrounding area. Studies from the 1960s already pointed to the phenomenon of heat island, but the effect is becoming more

Another way to verify the existence of heat islands is to make a parallel analysis of urban area temperature behavior as it moves away from its center and approaches a rural area. As shown in **Figure 5**, the first station away from the urban location is

**3. Study locations**

urban area and the rural area.

intense due to climate change.

**Figure 1.** *San Juan, Puerto Rico, annual temperature (°F) pattern for 2000–2019.*
