What are the chances my yeast are dead after shipping?

Ordered a vial of WL hefeweizen and an ice pack from AHS. Shipped on Monday night and arrived just a while ago. We've had some scorching heat in the central part of the country so I doubt the ice pack made it longer than one day. When the package did arrive it was smokin' hot so that wasn't very encouraging. Ice pack and vial were warm to the touch so I'm guessing they were over 100 degrees.

I always make a starter anyway so I know I will be able to eventually tell if any survived or not but I'm just wondering if there's a good chance they are dead if I should hold off this brew and do the other one I had scheduled this weekend. I just don't want to waste my time using the stir plate on yeast that might be dead when I could have used that time to work on a different starter.

I'd obviously rather get stated with the hefe this weekend first but I don't have any experience with shipping yeast in hot temps like this so I don't know how likely it is for them to survive.

Chances are, it's still good. Even if the viability % has been reduced, there will be enough to get a starter going. But, you'll have to do the starter before you will know for sure.

I always make the starter first, then decide when I'll brew, unless I'm dealing with dry yeast. I've probably got a little more flexibility than most brewers though, I'm not restricted to just weekends.

You should be fine. Recently did the same thing, and my yeast were fine (and I didn't even have an ice pack).

Second the starter suggestion. The yeast really should be able to survive up to around 120-130F. Always "proof" your yeast by using a starter, regardless of the situation. On a stirplate, you should see signs of fermentation within 24 hours. A small krausen may form, but you will definately see little tiny bubbles running along the side once the yeast take off. That's how I know that my yeast are finally active and I can relax.

It's unlikely you'll have total die-off.

I had the same issue a few weeks back Yeast Sauna. Pitched a started for both yeasts, they took off fine, pitched the start on my brew day and everything fermenting nicely.

Looking good so far. A little over 12 hours on the stir plate and it looks pretty active. Maybe I'll get two brews done this weekend after all