Hi Colly - with very few exceptions (and maybe never--I'd have to audit the code to know that for sure) no states are updated if the plugin can't download new data. I have several checks installed:
- If the plugin can't reach the WUnderground servers, it will change the Indigo UI device state value to "no comm" to indicate that there is no active communication with the servers.
- If the WUnderground servers provide data that are older than we already have (it happens) I don't update any of the states because we want to go with the last known "good" value.
- There is a plugin preference called "Skip Update if Data Are Estimated" (or something to that effect) which works off a key in the data WU provides. If WU says the data for that location are estimated--that is based on near-by data and WU's own algorithms--you can elect to skip an update. This is turned off by default if I remember correctly.
- Lastly, in some instances, WU will provide a value like [-99] or [--] which indicates that WU doesn't know what a good value is. In those instances, I provide [-99]. I used to provide a string that said the data were no good, but that broke people's triggers and scripts because they were expecting a rational number.
So I would say that you should be safe but you might want to put a lower boundary on temperature of -99F (or -57C) because we know that is a bogus value. If the outside temperature is going to actually be -57C, you probably have other things to worry about than cold floors! I would keep an eye on your stuff for a while to make sure that it works for you the way you expect. WU data have been known to be temperamental; I've added many traps to capture those cases, but there may be things that I haven't anticipated.