Over the years I have noticed that most alt season started as follows:
1. $BTC pumps first.
2. $ETH $BET & $LTC coin pumps next, leading indicators of the Alt season.
This year's alt season is a little different from all the alt seasons I've seen so far. Earlier in the alt season, the price of BTC has gone up, then the price of ETH and other altcoins has gone up in a short period of time. But this time the price of Altcoin has gone up long after the price of BTC has gone up.