This kind of climate can be divided into two categories based on the
average annual temperature.
_Warm_
The average annual temperature exceeds 18 deg. C. but the mean of the
coolest month is less than 18 deg. C. This sub-climate is characterized by
a short rainy season in summer and occurs on the west side of the
southern part of the Sierra Madre Oriental and on the Mexican Plateau;
it occurs also in the area northwest of Reynosa and on the east side of
the Sierra Madre Oriental but in these areas the rainfall is
irregularly distributed in the year.
_Cool_
The average annual temperature is less than 18 deg. C. but the mean of the
warmest month exceeds 18 deg. C. This sub-climate occurs only on the west
side of the northern part of the Sierra Madre Oriental.