[arinlen]

> "What was the hottest day in the past <variable time period>" will require you to start decompressing at $now-$period.

Your example relies on a query to retrieve all data points between timestamp A (X days from now) and B (now).

> - "I was so warm last night that I even woke up from it at 5am, what were the temperature and humidity then?"

What's your definition of then?

In time series, it's typically a statistic calculated from all data points within a time window. It might be max, it might be a percentile, it might be a summary statistics of some kind.