Don't know which weather service provides your other temperature read-out, but the one in sWeather uses Yahoo! (and its affiliated weather service).
With such different read-outs, it is safe to assume these are different. Which implies that they process weather data differently. Then there is difference in available data. Yahoo! is likely using weather satellites that keep track of weather in the US and rely on data from other weather agencies that cover different regions on the globe.
Is the discrepancy between read-out too large for comfort? Yes it is. But explainable, once you don't want to know about temperature read-outs in the US. AccuWeather is what my phone uses here in South-America, where I live. I found that to be a much more reliable source than Yahoo!, but AccuWeather charges quite some money to provide data through their API. Yahoo! doesn't. As sWeather is provided to you at no cost, you can't expect the author to pay for API access to one (or more, for averaging read-outs) weather service.
As far as I know, sWeather had to change to Yahoo!, because other weather services were charging too much or put limitations on API callls, which would make sWeather unreliable for everyone. Now it can be unreliable for people outside of the US, because of Yahoo!'s sub-par quality of weather data outside the US. And as the US is the main "market" for sWeather, I can understand and appreciate the choice for Yahoo! as weather data provider.
Besides all this, there is also the matter of weather satellites. Most of these were shot into orbit 15 to 20 years ago. Of those, many are starting to wear out, but there are not enough new satellites being made to replace whatever capacity is already there. Weather data quality is becoming more of an issue each new day. Weather data algorithms have gotten better since then, so that makes up a bit for loss of measuring devices.
Lots of words to explain that what the weather data you get from Yahoo! is nothing more than "best effort" when asking for temperature read-outs outside the US.