Learn Finnish: Parvekkeemme on lämmin ja valoisa.

To add a possessive suffix like -mme (our), you attach it to the word's vowel stem. For nouns ending in -e like parveke, the stem adds an extra e. This word also undergoes "reverse" consonant gradation: the weak single k in the basic form becomes a strong double kk in the stem. So, parveke becomes parvekkee-, and then we add -mme.

Could I also say Meidän parvekkeemme instead?

Yes. In standard Finnish, the suffix -mme already means "our", so the pronoun meidän (our) is optional. You can include it for emphasis (Meidän parvekkeemme). Note that in casual spoken Finnish, people often do the exact opposite: they use the pronoun but drop the suffix entirely, just saying Meidän parveke.

I recognize -mme from verbs like olemme (we are). Is it the same ending?

They look identical and both relate to "we", but they have different jobs! When attached to a verb, -mme is a personal ending that shows who is doing the action. When attached to a noun like parveke, it acts as a possessive suffix meaning "our".

Is the word valoisa (light/bright) built from the noun valo (light)?