Just like in the Koppen classification, tropical climate is based on the average temperature of all months being higher than 18 °C. This basically means that all regions classified as A in the Trewartha classification, are places with warm weather all year round.

The As subtype is characterized by dry period during the “summer” – this means during the period of longer days and shorter nights. It is a relatively rare subtype and just like the Aw subtype (dry winter), it is sometimes referred to as tropical climate of the savannas.

In general there are four savanna climate types:

• clearly distinguishable dry and wet periods of approximately same lengths. Most of precipitation falls during the wet period, during the dry period it rains only very little if at all.
• longer dry period followed by a relatively short wet period. In this case there are typically seven or more months of drought followed by five or less months with rain. This creates a relatively large variability and includes places with almost equal length dry and wet periods (5 and 7 moths), but also places with a very long drought and then very short wet period, which, however, is typical with very intense heavy rains.
• the third type is a relatively long wet period and a shorter dry period, in other words the exact opposite of the previous type. There are at least seven wet months and maximum of five dry months.
• the fourth type is very rare and is characterized by dry periods, during which however, it can sometimes also rain and so the difference between the dry and wet period is smaller than in the previous three types.

• warm summer: warmest month with average temperature between 18 and 23 °C
• warm winter: coldest month with average temperature between 18 and 23 °C