There are numerous programs and resources that can be used to ascertain pretty exactly the average temperature and general climate of a region.
But is there any way to get a quantitative estimation of rainfall or record high and low temperatures in a region?
I know general trends like, since my region is situated on the edge of the polar front, with an ocean to its east, high mountains to the west, and strong persistent westerly winds, it probably gets a considerable amount of rain. Or, I know that due to the lack of large landmasses to the north of my region, it probably will not have the comparatively cold record lows found in places like the NW US or Eastern Europe.
Finding an Earth-proxy isn't exactly correct either, since my reliable modelling for average temperatures suggest that the climate regime for my region is not completely equivalent to South Chile (my closest proxy). While these little differences may not mean too much for average temperature prediction, they can introduce unintended consequences to your world.
For example, Puerto Montt has the closest climate to my region's captial. They are remarkably similar in terms of year-round average temperatures and in rainfall (though mine shows less seasonality). However, in the winter months, Puerto Montt has an average low of roughly 3.5 C. My region's capital has average lows of 1.9 C in winter. This difference is negligible for getting a sense of the average climate, but it has a massive impact on other variables. With its milder winters, Puerto Montt experiences snowfall rather infrequently and sporadically, mostly in July. However, my region's capital gets 7-8 reliably snowy days a year that can happen as late as October, an event which rarely if ever happens in Puerto Montt. So, while proxies may be useful for parameters which are easily defined or that you can already predict, they are not useful for estimating other variables. I would expect record temperatures to be especially susceptible to this.
In short, qualitative analysis and proxies are insufficent. Are there any ways to get real quantitative numbers for things like monthly record temperatures?