Is there a unit that records the low temp and high temp during a given period of time? I testing gear , I'd like to know how cold it got during the night, etc. Thanks, Mark

Would something like this work for your testing ? Clearly it isn't designed for backpacking, but it is the lightest single piece, battery operated unit I could find that recorded min and max temperatures.
Link

coghlans digital dangler--min only to -10c --not waterproof---faint alarm--keeps good time--cheap

The thermometer Cameron mentioned looks OK, inexpensive too. If only I lived where temps didn't go below its range (-4F).

My friends at the MN State Climatology office are big fans of the I Button (it predates Apple's I-products so NO the name isn't an Apple ripoff).

It won't tell you the current temp unless you're packing a computer but it'll give you great accurate readings at regular intervals.

Thanks! I'll try the Dangler. Mark