Here is some information from an Energizer NiMH application guide. The first attachment shows that storing NiMH batteries at low temperatures significantly reduces the self-discharge effect. Here's some text from the application guide as well:

"Storage recommendations for nickel-metal hydride cells parallel those for nickel cadmium cells:
Store at the lowest feasible temperatures (-20°C to 30°C being the generally recommended storage temperatures).
Store cells/batteries open-circuit [completely disconnected from the device] to eliminate loaded storage effects"

The second attachment shows that a NiMH battery has highest capacity around room temperature. Any temps significantly above/below that will reduce the battery's capacity. I've noticed this now that the temps have really dropped. My bike light battery doesn't last nearly as long as it did during summer months.

Here's a link to the application guide itself. It has some good information; some technical, some not.

The temperature you're talking about (10F) would leave the batteries with about 40% capacity according to the graph. If it's a battery for a headlight which might get fully drained each day then definitely store it inside at night so you start off with a warm battery for longest run time. Since you need to recharge it regularly, perhaps daily, self-discharge effects are irrelevant in this case. If the batteries are for a blinky it's probably not as important since even at 40% capacity the batteries should last many days, assuming they're only used a few hours a day. You could probably get by with recharging them on the weekends. You'll have to experiment with that.

By the way, do you really leave your bike out in 10F overnight? Talk about a cold seat!