Looking forward to this in Guangzhou in late June (not).
Actually, 26+ dewpoint is at the top end of the scale for Darwin in April - don't think it's a record but probably not too far away. Will look it up at work tomorrow.
Now checked - the 27.2 at 8.30 this morning looks to be the highest in April since at least 1958 (and I don't really trust the extreme high dewpoints that far back). There are a number of 27.0s which look legitimate, although none since 1990.
Sunday peaked at 26.8, and Monday at 26.5.
Sunday's 26.8 mid-afternoon dewpoint was when it was about to rain (although the airport didn't record any precipitation, there were cloudbursts all around); would the theoretical dewpoint be exactly the same as the air temperature at a time when the relative humidity is exactly 100%, i.e. it is actually raining?
At 100% humidity, dewpoint does indeed equal temperature. It can rain at humidity below 100% (it needs to be 100% at the height at which condensation is occurring, but not necessarily at the ground), but normally humidity will rise to near 100% if rain continues for any period of time. It will also be 100% (or very close to it) in fog.