Thermometer fail when cooling wort

Just finished brewing my second batch ever, a petite saison from Northern Brewer. Everything was going along great, but my thermometer seems to have gone haywire during the wort chill-down. It showed the temperature steady at 84 for a long while--too long, I suspected. I stirred the wort, and it went up to 100. I rinsed the thermometer under cold water, let it sit at ambient temperature (about 58) in the basement), and the thermometer stayed up in the 90s. I checked with another thermometer, which showed the temp of the wort at 54. I went ahead and pitched my yeast. Should I just figure that fermentation will take longer than planned? Or....? Doom?

What was your method for chilling your wort and how long did you do it? If your worried about pitching at too low of a temp, my opinion is that Id rather pitch cold than hot.

I pitched at 60 degrees the other day. I haven't seen a single bubble come out of my airlock yet but I have a nice krausen on top. Fermentation seems to be less active when pitched at a lower temp. Primary has been between 65-70 since pitching. Low temp is ok, high is bad.

Thanks! I'll see what hapens.

It should be fine, low is OK, high is bad. I had similar problems during my first few brews, my thermometer could not handle much under 100 degrees. I now use a great digital one, I have a little write up here:
https://www.homebrewtalk.com/f11/best-digital-thermometer-314825/index2.html

Cool--thanks! AlcoSensored, I cooled the wort using method #2 that I read about here:

https://www.homebrewtalk.com/entries/cooling-wort-fast-without-chiller.html

It cooled the wort very quickly, if my thermometer was to be trusted at that point. It did seem to be working then. And about that thermometer: as the kids say, "my bad!" I read the instructions for the thermometer more carefully after the fact and saw I was not supposed to put it in water. Sounds like the wrong thermometer to me, even though the guy at the home brew shop had (nicely) sent me off to buy it at Target. Oh well! I will follow up on your suggestions, sniperd. Thanks again!

Cant get water in-between the probe and wire.
Had this happen to me yesterday, bent the probe if half and played boomarang with it!

If you have a polder(digital meat thermo) and an amazon prime account you can buy the probes for around 8$ shipped.
Lets just say i have a couple extras now...

Good idea to have a back-up!

I woke to that beautiful sound of bubbling in the blowoff rig, so all seems to be well.

I guess this was not so much a crisis averted as a crisis-that-never-was. Phew!