A cold snap in Denver turned my mortar mix into a real problem

I was laying brick for a garage addition last November when the temperature dropped fast overnight. I came back to a wall where the mortar was still soft and crumbly, not setting right at all. I had to chip out about four feet of fresh work with my pointing trowel, which was a real pain. I learned to always check the forecast and use an accelerator when it's near freezing. Has anyone found a good brand that doesn't make the mix too sticky?