I have a 2001 buick regal 3800 and when it'* cold out I set the cruise control, applied brakes for slower traffic, removed foot from brake and the car takes off like you were holding the resume. If you apply the brakes it disengages but goes back to acceleration when you remove your foot from the brake. It'* not the floor mat. If you shut the cruise off then nothing. Just acts like it engages tje resume on it'* own, like your holding the resume on. It will continue acceleration till you apply brakes or turn cruise off.

Sounds like the resume switch may be bad.

Switch cruise off then back on set cruise and ok. Only does this if outside temp is below 35 degrees. So probably not the switch. Just got it back from the dealer and they changed the brake pedal switch said everything else checks fine. Will see.

Actually there are two switches...one is a brake switch, and the other is called the cruise control release switch.....they both have to work for the cruise to function(one is normally open, the other is normally closed).....they are backups to each other...if the cruise control module does not see opposite values from them(zero volts and bat volts when brake pedal is release, and bat volts and zero volts when brake pedal is engaged), then the cruise is disengaged by the module......

There is no way the cruise control release switch or brake could be the problem, if the cruise disengages.....by that I mean, when you hit the brake, the brakes make the car slow down, and rpms should drop............

Since this only seems to happen under 35F while driving, you can rig up, any kind of a test light and have it positioned near the driver'* wiper so you can see it....ground one end....then get one of those wire piercing probes, and probe the grey wire(with black tracer) that goes to terminal "C" of the cruise control module(this is the resume circuit)......now attach the probe to the other end of the test light.....

With the key in "run" position, engine NOT running, cruise switch "on", press the resume button.....your test light should come on....when you release it, it should go off.....if it stays on, that is your problem.......

Now it may not act up until temps approach less than 35F........so you would have to drive it under those conditions with this hookup, and if you hit the brake, and the car takes off on you and the light is on(it should be off), then THE RESUME CIRCUIT is the problem.....that means the resume switch or the that circuit is somehow seeing 12 volts when it shouldn't, like maybe two chafed wires touching each other and one of them is a 12 volts source....

I forgot to mention that the other possibility is a binding/sticking throttle plate/bad linkage....