All the main English translations are supposed to be both technically correct and natural-sounding. We're trying to fix the ones that still aren't, so feel free to report sentences like that if you find them. That said, of course native speakers often disagree among themselves about what sounds more natural. :)
Weird, I replied to Rick's comment before but it wasn't saved.
Anyway, you're right about det är kallt här. The reason is that it's an adjective here, and hence kall needs to agree with det, which means kallt.
The noun köld, which is an en-word, not an ett-word, means cold as in "out in the cold". It does not mean the infection kind - that's en förkylning.
Thank you. My friend GT cheated on me. I suspected that the noun would be the opposite of the noun warmth. However, when I had "en köld" translated into Dutch I got something weird and "ett köld" became the mentioned infection. Conclusion: 1. my intuition was correct, 2. GT is really unreliable because every translation goes through English (cold is an adjective and a noun with different meanings for which other languages use multiple nouns and adjectives) and 3. GT cannot help with finding out whether something is an en-word or an ett-word.