Why some FNO expiry days are volotile and some expiry days are muted

Why in some FNO expiry days Nifty & BNifty are volotile and some expiry days are muted…most expiry days big movement which usually happens after 2.30 PM or so in my observation…Is there any ways to predict that which expiry day will be volatile…
Can we expect any difference in this volatility between weekly and monthly expiry days(Is it safe to assume weekly expiry days will be less volatile than monthly ones)…