Rainy weather already feels quite unusual as it is. It's a good part of the game. Players who's computers can't keep up sadly need to avoid confrontation during rain if it's an issue.
It's unfortunate, and trust me, I am -very- familiar with the reality of being simply unable to pay for computer upgrades, but it seems unfair to remove rain for everyone just because a few player's systems can't keep up with a 20 year old game, IMO.