I have a storage class written for the pi. It uses memcache (with fallback to files/mysql) for reads and memcached / files / mysql for storing data, wichever is available. I created it for a webservice that monitors 16 nut-capable upses and storring data for the last few days. I will upload it to github if you need it.
For what you need – to poll the weather service if it should trigger a rain delay – memcache is perfect. I will add to github a class you can just include in your project and just run the multiweather code as a service or cron.
Any bug reports / features requests are welcome.