5yr session distribution on the left, 20-day session distribution on the right, current session in the middle. 20-day is compressed relative to the 5yr. What does this mean?
This means recent volatility is below the long-term baseline. The market has been quieter than usual over the last month, despite the uptrend to new all time high. Currently in a compression / consolidation regime in terms of vol. Range bound tape, lower ATR, tighter daily ranges, etc.
Compressed vol historically resolves into vol expansion, and often violently. The trend continues until it doesn't, and when the regime breaks, you get sharp moves that blow through the narrow rolling bands. That's the "vol of vol" risk. Expecting outlier days here soon, don't let it catch you off guard when it happens.