Broadleaf weeds need to be treated with broadleaf weed spray. Nearly any garden center should carry broadleaf weed sprays, which go by names like Weed B Gon, Dandelion Killer, etc. Halts is a weed preventer, which can stop some of these weeds from germinating, but has no effect once the weeds have begun to grow.
The broadleaf weed spray can be applied anytime spring or fall. Summer in your area is a little too hot and risks burning the grass if you apply it at that time. So stick to cool times of year.
Halts is mainly used to prevent grassy weeds, such as crabgrass. Although its label will say it controls some broadleaf weeds, they germinate at many different times, so it's hard to control them with a weed preventer, which is typically applied in spring. That's why broadleaf weed sprays are the more common approach to broadleaf weeds.