Details on Freeze sensor

@json924  if you have SS3, not SS2, yes, you can set the temperature range to what you want.  You can use the keypad to do the settings.  Please note, I highly recommend you get the 24.99 plan, try it for a month and if you don't think its worth the money, you can call SS and downgrade to the 15 plan or cancel monitoring completely. Note, no partial credits, all billing is in monthly increments.

Here is the video how to in the Help Center.

https://support.simplisafe.com/hc/en-us/articles/360029869552-How-do-I-install-my-Freeze-Sensor-s-

@json924 officially indoor only but for the price, I would definitely try it. Don't know where you live, but I do have a SS3 motion sensor in my garage and it does just fine in Chicagoland weather where we can go anywhere from -35 to +95. Note your warranty is gone but in a crawl space I think it will be fine.

BTW, consider giving the 24.99 plan a try. I think you will think it's worth the money!

Note that the (SS3) temperature sensor can be set with a low of 0 and a high of 99.  There is no way NOT to have it alarm if either of those are exceeded.  You don't need any monitoring plan for it to work, although you would need monitoring to get alerted remotely that the sensor has been triggered.