In a dry spell the grass will stop growing but the weeds in the many lawns do not. The roller-first configuration of most cylinder mowers means that taller weeds escape the chop and return upright to taunt you after cutting the grass. There are two solutions - either use a rotary mower or modify your cylinder mower so it gets the perishers.
Most cylinder mowers have several wood or metal front rollers on a plain bar axle. Either take out all the rollers and leave just the two side runners as you can do on many Ransomes or Greens machines, or leave the two outer rollers and put a length of pipe over the shaft to keep them apart.
For example, many motor mowers over 24” cutting width have five or more rollers so the middles sections can be taken out. This way many of the bents get cut, though with a full grass box the two side rollers make marks on the lawn if it is soft.