Due to multiple factors, expect to potentially pay more when booking in September. For low rates, May can be a great choice for travel to Palm Springs. Flights to Palm Springs from Laredo in May are about $338 on average during May, but can be found for as low as $84.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Laredo to Palm Springs as you normally would.