If you missed out on catching Latias and Latios the last few times, you will get another chance soon as Niantic announce the Legendary Pokemons that will be coming back for the special Raid event this weekend.
The event will start on the 24th of January where both Latias and Latios will return and appear in five-star Raid battles. The pair will leave on the 27th of January so you only have a few days to catch them.
Being a Dragon and Psychic-type Pokemon, you best Pokemon to take into battle will be Ice, Dark, Fairy, Ghost, and Bug-type Pokemon so Pokemon like Togekiss, Tyranitar, and Mamoswine would be your best option now.
After this, fans can also try to catch Heatran which has been in the game for weeks now and will continue to appear in Raid battles until the 4th of February.