When describing something that is just above freezing but not quite hot, the term "barely warm" is often used. However, there are many synonyms for this phrase that can add variety and nuance to your writing. Some options include tepid, lukewarm, mildly warm, slightly warm, coolish, chilly, and cool-warm. Each of these descriptors connotes a slightly different degree of warmth, and can be used to paint a more detailed picture for your readers. Consider experimenting with different synonyms to add depth and complexity to your writing.