This looks like the last week we will have for delays (fingers crossed) as I think everyone I have checked so far shows night temps warming up above freezing next week . Just a couple places here and there that still look like it may be too cold to ship. In case you are curious of my process, what I do is check your weather forecast and look at the lowest night temperatures through the week. I try to ship packages when the temperatures during the estimated delivery timeframe do not dip below 22F. The insulated bag will give a nice buffer and help keep the temperature from changing too quickly inside, but it ultimately will not prevent it from getting too cold (or hot) with extended exposure. Most heat packs will add about 10-15F, however if temps are below 22F then even the heat pack could freeze. These little critters are pretty resilient and usually things are fine. They could even freeze for a short period of time, thaw out, and survive! I would rather not chance it though. At least not coupled with the extra day they could be in shipping due to the carriers still catching up a bit.
I know most of you totally understand and are completely fine with waiting until its safe, but I just wanted to give a bit more insight on the how and why I choose to hold a packages.