Isobars screenshot from San Francisco State University Meteorological Program website.
I will admit to being a magic skeptic. I believe that we do have the ability to change ourselves using magic, but I am doubtful about our ability to change the physical realm. I think weather magic is a waste of time: no harm, but no benefit either. That said, people who do weather magic believe in their ability to create change, so I'm going to meet them where they are at and assume they can impact the weather... and ask them to please not do so.
I'm not a meteorologist, but I've got an amateur interest in weather and weather systems. I watch isobar maps and FD charts. If you don't know what those are, you really have no business messing with the weather. And if you do know what they are, you probably already know better than to try.
Weather isn't something that just happens where you are. All weather is connected, and a weather worker does not know - cannot know - what impact their working will have on a neighbouring area or on the long term forecast in their own place.
It is raining in Vancouver right now because there is a low pressure zone sitting over our city. Lows like to settle in and linger, and they bring in clouds that press up against our beautiful mountains and drizzle on us for weeks on end. In contrast, simplifying greatly, high pressure zones push out clouds and result in sunny days. High and low pressures are not created here; we tend to get our weather from the north-west of us, and it moves over us and on to other areas. To create a sunny day here and now, one would need to pull a high pressure zone from somewhere else. If one could force a high front to rush towards us at great speed - to get a sunny weekend, for example - then low pressure zones would be spinning in to fill the gap, and high zones to fill those gaps, resulting in dramatic weather changes potentially all over the continent, and maybe beyond.
Do that over and over, and have different magic workers in different areas all pushing different weather systems around in all different directions, and who knows what will happen. It strikes me as an awful experiment, like finding out what harm burning large amounts of fossil fuels does by creating holes in the ozone layer. Pagans of all people should know how little we still know about nature and how we affect her. We should know that our personal desires are not justification for causing widespread problems: "an it harm none". We cannot be so selfish or short-sighted as to think that we can do something here and have no impact elsewhere; that's not how nature works in general, and it certainly isn't how weather works. We should know that everything is connected.
There may be circumstances under which dangerous weather magic might be worth the risk. If an area is undergoing flooding, drought, forest fires, or hurricanes, maybe a case can be made for magical intervention (though I would still argue that we may make things worse and not better; well-meaning interference could result in a game of magical weather wack-a-mole). However, a sunny weekend for our pleasure and convenience is not reason enough to mess with something so complicated.
We've got a weekend Pagan camping trip coming up this weekend, and I know it will be more fun if it is sunny out. We're lucky that our camp has cabins; no one will have to deal with a wet tent. I am still hoping that the high just to the north-west of us moves down in time, opening up the possibility of frolicking and circling in the sunshine, and maybe even to do a bit of swimming, but I think it would be unethical to try to do anything to urge it on.
I also wonder why Pagans, at least of the nature-worshiping type, would want to mess with the weather. If we want to honour Mother Earth, if we want to stay in touch with the seasons and with nature, than we have to accept some rain and cold, even when it is inconvenient. If you want a climate-controlled temple, there are plenty of religions who provide that; please don't adjust the thermostat in your local forest.
