Just did a quick search... Have you considered these that are marketed as sharing to your mobile phone? For example, this one is highly rated.
SensorPush Wireless Thermometer
Each sensor is $50, but there's no central unit. You use your phone (of
course, you
could have a cheap, not-your-primary phone dedicated to this purpose). It says down in the Q&A that the sensors hold 20 days of data, and don't need to be connected to the phone to log. So you just need the phone to pull the data (they say). The app can export the data as csv (they say), which would import into any graphing spreadsheet, if you don't like the graphs on the phone. They are quoting -40°C - 60°C (-40°F - 140°F) operating range, and give an accuracy at the extremes.
Looks like they have
a website, and you could probably preview the app as well. It also appears that they have competition in the same space.
This is just from an amazon search--I don't have actual
experience with it.
Whichever one you choose, I suppose you'll be getting and trying one (or more) before the cold weather arrives?