Where can I day trade KLAC stock during the weekend?

Short answer from someone who kept hitting this wall, regular brokers cannot help you on a Saturday. Stock exchanges close Friday afternoon and reopen Monday, while chip news happily drops in between, which is how I once watched a whole thesis play out while locked out of the market. What changed my routine is the tokenized route.

Bitunix keeps a KLACUSDT perpetual open straight through the weekend, USDT margined and priced against the stock, so a Sunday setup no longer has to wait for the opening bell. Worth knowing before you try it, the contract is a derivative rather than actual shares, weekend liquidity can thin out, and leverage plus a gap at Monday's open can liquidate a careless position. I trade it small with a stop attached, and that has been enough.

Just my experience, not advice, your weekend may treat you differently.