This.
I have used FSD in a lot of heavy downpours both in daylight and at night. Never a problem and at night it's extremely helpful. Only once with V12 did FSD disengage and that was when at least 25% of the cars on the highway pulled over to the break down lane the rain was so hard. Perhaps the hardest rain I've ever driven in. Cars that stayed on the highway were going less than 20mph. HW4, Model Y.
Hokay. I've had two memorable trips through serious rain over an extended distance. Note: A drizzle to normal folks at a standstill is quite a bit of water hitting the windshield when traveling at speed. FSD(S) reacts to the amount of water, natch, not the precipitation per hour numbers.
#1: Through the remnants of a hurricane blowing itself out through Central Connecticut and Central Massachusetts, on 11.4.9:
- Start: Light rain hitting the windshield, one gets the Warning Message about the driving being degraded. Speed set to 5 mph faster than the limit, which is the speed at which most people are traveling.
- Rain picks up. At this point, one can't go faster than 5 mph faster than the limit.
- Rain picks up some more. At this point, the speed limit that the car will travel on is limited to the official limit. So, if one is on a 65 mph road, one is not going faster than 65. Not Really Helpful if the semis are going faster than you are.
- Rain picks up some more. The speed limit the car can reach is now 5 mph slower than the official limit. So, at a 65 mph limit, 60 mph is what the car is limited to. This is a real problem since nobody is really slowing down. With a significant amount of water on the tarmac, trucks in particular kick up huge amounts of spray, leading to:
- Rain/spray picks up some more. The car says, "FSD is disabled due to weather". In other words, it gives up.
At this point doing the shift-lever stuff into FSD fails, period. Oh, well, it's coming down pretty heavy. At about this point normal traffic starts to slow down a bit due to the spray from all the semis which reduces visibility. This tends to be bad for cars and SUVs, but the semis, with the drivers perched 'way up there, have better visibility and tend to not slow down.
After turning right into the Mass Pike/I-90, the rain started to lessen, until by Worcester it had pretty much stopped. The above bullets worked in reverse order as the rain decreased.
#2: On the way to Texas through the Shenandoah Valley, through a North-Easter (i.e., a storm heading up to New England, taking I-81 to do so).
Pretty much the same as #1. Unlike #1, though, was traveling in the opposite direction of the storm, so got through it faster.
My opinion about all of the above: Tesla development is madly working on getting 12.x/Robotaxi fully functional. Sweating poor visibility, beyond making sure that users transition more-or-less gracefully into
them doing the driving, is probably not their highest priority. Once the March of 9's truly begins (and, yeah, there are posters here who think that that's never going to happen), there'll be staff freed up to handle poor visibility.. which is something that I think NNs can handle without too much trouble, just like
we handle poor visibility without too much trouble.
Speaking of that: Despite being a long time resident of the mid-Atlantic and New England, with the occasional fling in the South East, the scariest driving I've ever hand to contend with hasn't been with snow, rain, sleet, and hail: It's been these ridiculously thick fogs going up and down I-65 in Indiana. Landscape as flat as the dickens with the fog so thick that one can't see the tail lights of cars and trucks more than 100 yards up and no, I'm not kidding. Worse, the semis don't bother slowing down, so
they're blowing through at 65 mph - so if one slowed to, say, 45 mph or so which would be safe, a speeding semi coming up behind one would flatten the car one was in with no trouble at all. Under these circumstances, the safest way to travel is to get behind a semi so one can just make out their taillights, then keep up. Hopefully, if they get into a crash, given their longer stopping distances, one would have time to stop and then get 'way the heck off the road before the next bunch of speeders comes down the pike.
Despite my comments that Vision Should Work OK, this is the One Place where a RADAR would be useful. Maybe. Except that if a RADAR on one's car stops the car in time, it won't do a thing for the non-RADAR vehicle coming up one's backside in the soup.