Which tool is least in predicting weather

There's one weather forecasting technique known to meteorologists as 'persistence.' Persistence means 'what was...will again be." In other words...today's weather will also be tomorrow's weather.  

In some places...that's not a bad technique.  

Think of sunny southern California where the weather is pretty much the same day in and day out.  

In most places...on most days...the 'persistence' technique would be the least useful tool to predict tomorrow's weather.

I hope this helps :)

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).