I’d make an educated guess that you have a WiFi Only model iPad…
Unlike your iPhone that has GNSS/GPS capabilities - WiFi Only models of iPad have no GPS capabilities with which iPad Location Services can derive precise location.
WiFi Only iPad models can only “infer” their location from a database lookup of neighbouring WiFi networks for which the geographic location is known, or the geographic location of your public IP address. For static applications in urban locations, where the location of IP public IP addresses and WiFi networks are known, while imprecise, an “inferred” location can be “relatively” accurate. However, in rural locations, or when using a Cellular/Satellite/VPN connection, location accuracy of an inferred location [if it works at all] may be very inaccurate.
As such, the Weather App on your iPad and iPhone may have a similar - albeit different - idea of location. Apple’s “hyper-local” weather forecasting models are very sensitive to location - and this may account for the differences that you see.