How do you keep your fingers warm?

Practice and rehearse in rooms above 17°C. 

Our rehearsal room is heated. For cold outside gigs, I use fingerless gloves with heating pads.

Go to a sam's club or Costco and get a box of hot hands. When you're not playing, put your hands in your pockets with hot hands.

Get a space heater for your jam spot.
Find a new jam spot that isn't so cold.

Set your bass on fire mid-gig

“In the pocket”….

Fingerless gloves if I'm playing outside in the cold.

Put them under a warm tap every so often

You should try playing upright when it's below 45---absolute nightmare

I bring a fluffer

Do you rehearse outdoors in the cold?

I tend to warm mine up with a cold beer. I also live in the south so I have never needed to warm or think about my fingers during those situations. Indoors is heated and I don't think I have ever played an out door gig below 50°F.

Dunno, some people play with gloves on. Put some HotHands in there.

I've used those gloves that Scott uses
https://scottsbasslessons.com/

They are thin and fit well which means they don't mess with your fretting articulation. They might even damp some of the unwanted ringing.

Once I'm warmed up, my fingers tend to stay warm as long as I'm playing. To warm my fingers up initially, taking a shower works, and so does putting my hands in a bowl of warm water.

drinking an playing.

I played outside last year for a Christmas party, we were inside a tent just. I could hardly move my fingers for two songs. Next time bring mittens.

Cram them in my ass between songs

where we rehearse it always gets very hot very fast. It ain't weird sight for us to bring a pair of shorts in the winter and we stand there, in shorts and no shirts while outside it is below 10 degrees

Play faster

Practice/rehearsal, no issue, I don't practice or rehearse outside. Simple as.

If we start playing outdoor gigs when it's freezing outside...I'll probably need to have a conversation with our bandleader.

If I've absolutely GOT to play somewhere it's cold, I guess I could switch to using a pick. Can still hold one of those with gloves on. Fingerless gloves for fretting hand?

I don't think I could fret properly with any glove that would keep my fingers warm. Skill issue I suppose. :/

I use a heater in the room.

Failing that, fingerless gloves.

In High School I worked in the produce department at a local grocery store. The backroom was refrigerated and I'd be stuck there for hours processing [wet] vegetables. I found warming my hands on my neck works the best.

Get some heated fingerless gloves?

play fingerstyle so fast that i generate heat

Fingerless gloves

By any means necessary!! 😂
Seriously though I have had this problem my whole life. Fingers and toes get stiff and painful in the mildest of cold temps.
Hot water helps if you have access.
I was actually able to find a pair of lightweight fingerless gloves that I can play in, compression gloves for players can help too. Good luck 🍀☮️💟🤘🏼😎🤘🏼

wtf? Is your circulation okay? Are you playing in storage sheds? I’ve played countless hours of music in Boston and have yet to have the weather be an issue.