Sorry Brian... I missed this the first time! When I ship, I check the temperatures not only here and the destination, but the UPS Sorting Hub as well. For summer shipping, I will not ship if the temperatures are over about 90-92 degrees at the destination. A cool-pack will only keep the interior of the box cool for the first part of the journey. If the destination temps are too high, you can work it out with the customer to have the box held at the UPS Customer Counter for them to pick up... that way it doesn't sit in a super-heated truck while it goes out for delivery.
For cold weather months, I will not ship if the temps fall below 38 degrees. A heat-pack will keep the interior of the box warm for up to about 20 hours, and reach it's peak usually within the first 6-10 hours.