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Hiking up sunny, rocky trails in Cloverdale, CA in 100 degree morning weather and spending the day’s 106-108 degree heat playing and jumping into swimming holes in the Russian River, finding shade under random scrub and digging in the mud. Backpacking as a 7 and 8 year old at 8000 feet elevation up blazing hot switchbacks and trails in the Sierra Nevada in the full summer sun to arrive at a secluded lake 5 miles in by late afternoon, with our 2 Siberian Huskies (yes, the full coated sled dog) happily trekking along and snooping out marmot dens. Taking long hikes when temps were in the 90s with our huskies in Death Valley, exploring almost every canyon there. <modsnip>
They (NPS) want families being active and enjoying the outdoors. And they have advice and guidelines about how to hike in extreme temperatures (not limited to age or infancy) and do it safely.
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As a young child (and I’m sure as a baby), I did what these people did. A hot summer hike to a cold river was the BEST. To be sweating and hot and looking out for rattlesnakes and just about to start being miserable, and then finally being able to plunge into cold water! For some people, that’s the stuff of life.
I don’t judge my parents badly for those experiences. I never felt unsafe, and we and the dogs always had plenty of water. There were certainly times on hot switchbacks carrying a backpack on my tiny legs that I complained, even cried, asking “When are we there!?” But I learned that struggle is just part of life and can actually be very gratifying, and the rewards are so worth it.
I’m forever grateful to my parents for getting me out there, often in what might be termed extreme conditions, safely and with love.
Respectfully, I don't think you did quite what this family did. In the 106-108 temps you were cooling off in the water, and you hiked switchbacks at high elevation, where it was a lot cooler than their low elevation. The conditions aren't the same. That said, your outdoor experiences sound wonderful and I see why they're so meaningful to you.