Two big Denver concerts slated for February 1 aren't happening: Miranda Lambert has rescheduled her arena gig, and Michael Kiwanuka canceled his show entirely.

Too ill to perform, country star Lambert, who was scheduled to play the Pepsi Center in Denver tonight, had to back out, rescheduling the concert for March 2. All tickets will be honored on the new date.

Lambert also rescheduled yesterday's January 31 concert in Salt Lake City, posting the following explanation to Facebook:

"I am so sorry I am having to reschedule the show tonight. I've been doing everything in my power to be 100% but my voice is just not there. Not even close. I am so sorry to let everyone down. Since I'm not well, we thought it would be better to come back and give y'all the best show we can," she wrote.

"I am medicating and resting and praying I will be better to play Denver tomorrow," she added. "Thanks for understanding and please know that my heart is broken over this."

Fans have been supportive.

"I’m in Denver and I’d rather have you reschedule than have a crappy show," one weighed in, adding, "no offense."

Another wrote: "I have tickets to the Denver concert. I've been to every one you've had here. I'd rather you be healthy and all in, not just for our sake, but for your own, so you don't get any worse! Please take care of yourself and feel better! #AlwaysLoveYa"

Traffic forced Kiwanuka to cancel his February 1 Denver gig at the Gothic Theatre after an accident shut down I-80, making it impossible for him to arrive on time.

"Denver we are incredibly sad," he wrote in a statement. "A major traffic accident on interstate 80 turned what should have been an easy drive into a mess. Fortunately, neither Michael nor anyone on the tour were involved in the accident, but after looking into all options available, it is unfortunately impossible to make tonight’s concert at the Gothic Theatre. Denver you are awesome and it’s a priority to come back as soon as we can. Refunds will be processed."