"It is hot."
Translation:Il est chaud.
Another duolingo user pointed out this helpful blog post on the topic of when to use 'c'est' versus 'il est'.
This is an oversimplification but...
He is / She is + adjective -- use Il est / Elle est
He is / She is + noun -- use C'est
In expressions where you are giving your opinion about something in the phrase "c'est + adjective", I believe you always use the masculine form even if talking about something feminine.
Que pensez-vous de ma robe ? (What do you think of my dress?)
C'est beau ! (It is beautiful!)
Kristynka- Mere_des_chats is correct. You may want to take a look at this blogpost.
The relevant excerpt is point 3.
Below is part of point 3 from that blogpost.
3 – C’est + adjective masculine singular
To make a live comment, react to something, share your experience, we use the construction
c’est + adjective masculine singular.
It’s your emotion that comes through, not a specific description. C’est beau ! c’est bon ! c’est chaud !
Watch out that the adjective cannot be in another gender/number ; c’est belle is not possible, even if you are looking at “la mer”(the sea). The construction demands a masculine singular adjective.