Cold glass and a wet pit will not take a clean resin cure
Water in the break goes milky. Freezing glass grows legs and slows the lamp.
Resin wants a dry pit and a glass temperature the lamp can finish. A car that sat in rain with an open chip holds water in the cone. Inject over that water and the fill clouds. The vacuum step exists to pull that moisture out. Skip it and the repair looks worse than the break.
Below freezing, two things happen at once. The glass is slow to take a cure, and a crack that was stable in a garage can run on the drive to the driveway. Mobile techs in freezing cities often want the car inside, or they schedule the replacement instead of fighting a soaked star at twenty degrees.
Heat has its own failure. A windshield that has been sitting in desert sun can be too hot for the resin to flow the way the bridge expects, and a star that was short at dawn can pick up a leg by the time the van arrives. Measure on arrival.
The useful notes from the caller are simple: is the chip wet, can the car come indoors, and what is the outside temperature if they know it. A sunny, dry bullseye is a short visit. A soaked star in a freeze is usually a windshield.
A dry bullseye at 70 degrees is a short resin visit. A soaked star at 20 degrees is usually a replacement, indoors or on the driveway.