Since weather conditions typically affect areas encompassing multiple square miles, the Storm Shield app uses the Apple Significant Change location technology. This minimizes battery consumption while still determining if your location will be affected by the weather condition.
A single "peek" at your location will generally be accurate to within 3000 meters (~1.8 miles).
This accuracy may be improved when there are multiple cell towers in your immediate area and when multiple WiFi zones are available. The Significant Change service can subsequently narrow your location to within a diameter of 100-500 yards (~1/4 mile).
If your device has WiFi capability only, your location may actually be identified as the ISP distribution node only within the first "peek"; which may be several miles away.
No further accuracy is required (and no further battery consumption) to determine your weather environment.
Note that other apps (such as the Apple Phone Locator) may provide much tighter location references and may disagree to some extent with the Storm Shield positioning coordinates. The objectives are different, as is the price they "pay" in power consumption.
So, if your "Current Location" is consistently showing up in the same place, but this is actually offset from your "true" location, it is most likely the result of the "snapshot" used by the Apple service. Because the snapshot is intentionally brief the resulting location may be impacted by geography, number and proximity of cellular towers (as well as the actual traffic load on each tower), clarity of line-of-sight to GPS satellites, the ISP distribution point, and many other factors.
The important factor is that you are shown located within an affected weather area.