This is the 4180th most frequent Polish word.
ciepły
Warm.
In this sentence, "ciepły" functions as an adjective describing the temperature of the day.
Dziś jest słoneczny i ciepły dzień.
Today is a sunny and warm day.
Here, "ciepły" describes the coat as providing warmth, emphasizing its function to keep the person warm.
Załóż ciepły płaszcz, bo wieczorem będzie zimno.
Put on a warm coat, because it will be cold in the evening.
In this context, "ciepła" (the feminine form of "ciepły") metaphorically describes the conversation as pleasant, friendly, and emotionally warm.