Life How long does weed stay in your system? What smokers, new and old, need to know. July 22, 2022April 28, 2023 Liam Gravvat, USA TODAY Comments Off on How long does weed stay in your system? What smokers, new and old, need to know. Weed will stay in your system, with noticeable effects, for several hours. Some drug tests can detect it for longer.