When there is snow, most likely, but the Notch is wonderful to visit any time of year. Also, in case it wasn't already clear, you can't actually drive up to the notch. You park at Manker Flats or at the bottom of the ski lifts and then either hike up (about 3-3.5 miles on dirt road) or take the ski lift up (about 15-20 minutes IIRC, check the website for cost).
As mention, you only need them when it snows. You can always check out their website and they may place the warning on there when you need them.
When there is snow, OH Yeah.
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