Temperature varies by elevation and these parks reach from 1500' to 14,494' (457m to 4418m). Therefore, conditions change drastically depending on where you are!
Some roads close, others may be icy. Chains may be required. Call for the latest conditions: 559-565-3341. If you visit between November and April, snow may close the Generals Highway, the park road which connects Sequoia with Kings Canyon. Depending on your destination, road closures may force you to drive around outside the parks to another entrance. To prevent this, call the parks from the Fresno or Visalia areas just prior to arrival to check on road conditions.
If your winter destination is Sequoia National Park (including Wuksachi Lodge and the Giant Forest), you are least likely to encounter road closures if you arrive via Highway 198 through Three Rivers.
If your winter destination is lodging or snowplay in the Grant Grove area of Kings Canyon National Park or snowplay or lodging in Sequoia National Forest, you are least likely to encounter road closures if you arrive via Highway 180 through Squaw Valley.