Shipping from very cold to warm

Hello! I'm supposed to ship a gecko to California next week, and our temps here just dropped. Next week will have lows of 16F to highs of 29F. I have the white shipper's box with the thick styrofoam lining, peanuts, delicup and heat packs. Is it safe to ship now that the temps here are below freezing? Should I use one or two heatpacks? How should I package it in order to keep the gecko warm enough on this end, but not bake it at the warmer destination?
Thanks!

There are a number of variables, including the particular animals and the box size. Too large a box leaves you with a lot of space to heat, even if you fill it with packing. Too small, and the animal ends up too close to the heat packs. Is it safe - yes, if you do it right. It's kind of a balancing act, but you can do it by using different combinations of heat packs - some heat up faster and cool off sooner. I don't keep a bunch of different ones on hand, so what I will do is start a pack earlier in the day so it boosts the temp during the early part of the trip but wears down before the end (depending on variables, another pack is usually added just before sealing the box for shipping). It pays to get a feel for the destination temps too...it may not be as warm as you think when they get there (check weather.com's hourly forecast).

One thing that I have found helpful is to get feedback from the recipient about the temperature when they open the box - an actual temperature is awesome, but being told the animal was warm or cold helps. (I recently used a slightly larger box but neglected to add a 2nd pack because the temps were fairly mild - thankfully, I was told that the contents were cold on arrival).

I would still put several heat packs in cause even here in California it is pretty cold... Wrap them up in several layers of paper towels or cloth so that it isn't too hot.

yep, got freeze warnings here in sunny northern California. Brrrrrr.......