Tom, the plastic containers it comes in aren't bad on weight/volume. And the lids are pretty secure.
If the amount you're planning to use is more of less than the factory plastic container, increase or decrease it in your menu so you use exactly a factory size. Take the aluminized foil seal off the top of the jar before starting out so you're not carrying it the whole way.
Or get through a container with 1-2 days left and use the container (which admittedly doesn't compact well) as a trash container.
And +1 on everyone above – ambient temps are just fine.