Cálido vs. caliente vs. ardiente
The Spanish language, like many others, has a variety of words to describe various temperatures. The words 'cálido', 'caliente', and 'ardiente' are close synonyms that can all mean 'warm' or 'hot', but they are not interchangeable and each conveys a unique nuance.
Cálido
'Cálido' is generally used to describe warm temperatures that are pleasant or comfortable. It tends to refer to atmospheric temperature.
El clima es muy cálido en primavera.
(The weather is very warm in spring.)
El sol proporciona un calor cálido.
(The sun provides warm heat.)
Caliente
'Caliente' distinctly refers to something hot, often to the touch. It is most commonly used to talk about tangible objects or food.
El café está demasiado caliente.
(The coffee is too hot.)
No toques la estufa, está caliente.
(Don't touch the stove, it's hot.)
Ardiente
'Ardiente' literally translates to 'burning'. This word is mainly used for extremely hot temperatures and can also convey an element of danger.
El fuego es ardiente.
(The fire is burning.)
Los rayos del sol son ardientes en verano.
(The sun's rays are scorching in the summer.)
Summary
'Cálido', 'caliente', and 'ardiente' are three Spanish words that denote various degrees of heat, with 'cálido' often referring to pleasant warmth, 'caliente' more so towards notable heat or hotness often related to tangible objects or food, and 'ardiente' implying an intense, potentially dangerous level of heat such as a burning fire.