Techniques are disclosed for estimating a surrounding in which a mobile device is situated based on sensors of the mobile device. The sensors can be typical sensors currently existing on mobile devices and not dedicated for surrounding detection purposes. One embodiment includes a method which comprises retrieving a weather condition from a remote server; deriving, based on the weather condition, a plurality of weights for sensors on the mobile device; applying each weight to an output of a corresponding sensor on the mobile device; and determining whether the mobile device is likely to be indoor or outdoor based on one or more weighted outputs from the sensors. Among other advantages, embodiments disclosed herein increased accuracy to estimate the mobile device's surrounding without the need of dedicated sensors or other modification to mobile network infrastructures, thereby providing the benefit of surrounding sensing without incurring the cost.