They've done test days that early in the past, it's hit and miss. I've spent the whole weekend in late April hanging out in the trailer or working on bikes because it was too cold to ride. Even the round in early May can be tricky.
They held a CSBK Rd1 there in late May 2006 and it snowed on Sunday morning during practice sessions.
I recall getting everything packed up in preparation for test weekend on the last weekend of April but knowing that the forecast was iffy, getting up at 4:30 AM regardless. Went out the door then slipped and fell on the sidewalk which had been coated in freezing rain. Limped back inside and crawled back to bed.
IIRC a few people showed up regardless, but no one rode. First round and last round can be iffy.
It's great to see that there are no conflicts between RACE and SOAR, VRRA, and CSBK (actually I think one of the RACE rounds conflicts with SOAR's practice weekend, but that's no big deal). 3 out of 4 VRRA rounds conflict with a SOAR round, though. A friend of mine is planning to do the entire SOAR endurance series so that's where I'm going.
I might make a one-weekend return to RACE after several years absence ...