In reply to Derry:
That's pretty awful luck.
In general, the late winter/early spring weather hasn't been anything to shout about in Catalunya compared to some of the years I've been here, but all that changed a couple of weeks ago and since then it's been wall-to-wall sunshine — actually hot enough to send people scurrying at times.
You don't specify the dates of your forthcoming trip, but looking at the local forecast from this Thursday onwards, covering the first half of next week, presumably you're arriving this weekend?
As you've already booked accommodation near Montserrat, the (generally) drier western side of Catalunya is unfortunately out the equation unless you're prepared to add a 3-4 hour round-trip drive to your day.
The only positive advice I can give is to look to the southern aspect of Montserrat rather than the northern. Many of the sectors on that side are lower-lying, sunnier (obviously) and therefore much quicker to dry out.
Pete.