This is the 13963rd most frequent Spanish word.
suben
"Suben" means "they go up" or "they ascend."
In this sentence, "suben" is a verb in the present tense indicating the action of ascending, performed by the plural subject "los niños" (the children).
Los niños suben las escaleras rápidamente.
The children go up the stairs quickly.
Here, "suben" refers to the increase in temperature, used metaphorically to describe how the temperature levels ascend.
Las temperaturas suben durante el verano.
Temperatures rise during the summer.
The word "suben" in this sentence describes the action of an increase in prices, indicating that the cost ascends.