JetBlue TrueBlue - Rainy Day Service from JFK-LAS - What to Expect?

So I have a flight on the 6:30PM flight from JFK-LAS tomorrow night, and the weather for NYC is supposed to be rain all day tomorrow, with winds at 15MPH.

I have never flown before where it is raining when I leave and I was wondering if anyone had flown Jetblue before in the rain from JFK and what's to be expected.

I know wind always causes delays, but does rain with no wind cause a lot of delays. Can planes take off if it is raining?

Also, how does standby work if we wanted to take the earlier 2:50 flight. I was told Jetblue will let you take the flight before for free if there are open seats. Is there any way to confirm a seat within 24 hours of the flight, or do I have to just show up and hope there are open seats. I figured that even if the 2:50 flight is delayed, it would be better than th 6:30 one being delayed (which is the last Jetblue flight of the day, and I have an appointment the following day).

Sorry about the long post, just a nervious flyer, somewhat inexperienced flyer here. Thanks.

Planes fly fine in the rain. The problem is that they have to space themselves out a bit more than normal jsut to be safe. That extra spacing slows things down from optimal operations and that causes delays.

As for the standby option, yes, you can get on the earlier flight but you have to do it at the airport.