Rahu, the north node of the Moon, will be in Punarvasu Nakshatra from January 2nd, 2019 to September 11th, 2019. Note that Rahu and Ketu change signs on the same day but they do not necessarily change nakshatras on the same day. Rahu moves into Punarvasu on Jan 2, 2019, as per the mean node calculation.
Punarvasu pada 4 lies in the sign of cancer but Punarvasu pada 3, 2 and 1 are in the sign of Gemini.
Here are some videos explaining how this transit will impact you based on your Moon or Ascendant sign.