Skiing, etc.
Not afraid of freezing your assets? Skiing season has just started as winter is here to stay. Until spring.
Many of the numerous ski slopes in Latvia are located near Rīga (there are a couple in Rīga too) and offer equipment rentals too. Just pick what seems right to you.
Cross-country skiing in Rīga:
The two municipal distance skiing tracks are located in Uzvaras bulvāris 15 (central) and Purvciems (not so central) and offer equipment rentals for €4.50 an hour (adults). The tracks are open from 10 a.m. to 9 p.m. each day.
Another skiing track is at Mežaparks.
Ski slopes/snowboarding/etc. slopes with ski lifts, outside the capital:
Milzkalns west from Rīga; Riekstukalns near Baldone; Kaķīškalns in Sigulda; Žagarkalns near Cēsis; Reiņa trase in Sigulda.
Ice skating
If you prefer this to that, there are a number of options too: municipal ice rinks have opened recently with one just by the Congress Hall (equipment rental is cheap), one at the aforementioned Uzvaras bulvāris 15, one on the Spīķeri square (Maskavas st. 4), and several more across the neighborhoods of Rīga.
Orthodox Christmas
So many, many people are celebrating and worshiping on Orthodox Christmas over the weekend that it'd be impolite not to mention them.
A number of religious concerts will be held across the country too but to pick just one the GORS hall in Rēzekne will host the Estonian Philharmonic Chamber Orchestra under conductor Kaspars Putniņš.
They will perform pieces by Arvo Part, Rachmaninov, and Alfred Schnittke.