The shipping of medical material is always the most complex and delicate of any delivery, and the hotter it is out the more important it becomes that everything is executed perfectly. Most medical material is very sensitive to the heat, and if exposed it can become damaged or destroyed based on the length of the exposure, and the temperature. That is why a San Francisco delivery service that is permitted to make medical deliveries must have special equipment and training to ensure that they always prepare the cargo properly for shipping.
The most important thing is that the material is packed in temperature insulated containers at all times. The vehicles which are used to transport medical material are all temperature controlled in a variety of different ways. Some are refrigerated or air conditioned, and others are complete freezing units which carry goods that need to be moved while not just cool, but frozen.
The individual packages need to be insulated as well though. When it is very hot outside, even a brief exposure to the elements could be very damaging to the shipments. As long as the packages that such material is placed in is sufficiently insulated though, the courier should be able to complete the delivery quickly enough that the temperature inside the containers shouldn't have time to warm up to match the external temperature.
Another important part of preparing medical material for transport in the heat is making sure that you have an indoor location where the cargo can be loaded and unloaded from the vehicles. Obviously, you can't always control this, but if you can make it happen you can greatly reduce the chance of damage happening due to heat by being out of the sun and in a temperature controlled environment any time anything is being handled outside of the cooled trucks.
If you're looking for a medical courier, be sure to ask them what steps they take to make sure that your medical goods are exposed to as little heat as possible. Taking the time to do your due diligence with your courier companies might be the most important part of preparing your cargo for shipping. If you find a company that makes sure to follow all of the best practices when it comes to shipping medical cargo you can be sure that your shipments won't become damaged, making sure in turn that you don't become liable for shipping low quality or damaged goods.