Last min CX question - warmup, how long prior for it to still work?

So I have an afternoon race today, 3:50 (the elites get a night race under the lights, RIP Gloucester this weekend)

Thinking of trying something different and doing an opener workout prior to my leaving home, I’m about 45mins from the venue, I’m thinking maybe it’s too soon and leave me with too much downtime to benefit come race start, but interested in thoughts. Warmups are maybe the one thing that I say I do really badly for CX racing, so trying to get a little more focus on it, since I generally don’t get more than just a casual course preride prior to events.

I would think any warmup you do at home would be way too early to be of any use for the race, but I’m willing to be wrong. I have considered it, but never bothered to actually try (extra shower, another set oof bibs to wash, etc…). Pre-race warmups are definitely something I’m also horrible at. I usually get my preride in as a bit of effort (but not race pace) about an hour before my race, but I’m definitely cooled down by then even after noodling around a bit.

Yeah, I don’t really see doing something 3hrs prior as really being helpful, I think any effect would wear off by race time. Just slightly curious if doing something even a few hours out and then preriding would be better than preriding alone. I keep meaning to bring my road bike and trainer to warm up, might finally get around to trying it.