Assuming you're not headed for snow or alpine conditions, you can compromise by checking the condition of your tent, investing a few bucks in a bottle of seam sealer, and taking plenty of tent stakes to ward against wind. If a down sleeping bag has lost loft, check into stores that can inject fill to increase warmth. Larger camping stores often rent out such equipment. Plus, they may offer free clinics on backpacking techniques, backcountry first aid, and map reading. Finally, don't forget to check the weather forecast before heading out, and again at a local ranger station, which may have more detailed information.
Meteorologists can sometimes make mistakes, but some information is better than none.
I doubt the weatherman could have predicted the tornado that touched down a mile from our pine tree-sheltered campsite one autumn evening, but he probably mentioned the storm system headed our way on the six o'clock news. Dorothy and Toto whirling around in our tent. Fortunately, we had left our itinerary with my mom and signed the hiker's logbook, so the rangers would have known where to find us had anything happened to us. Once on the trail, clothing layers enable hikers to regulate body warmth by peeling off or adding layers as the weather or exertion demands. I prefer layers that button or zip, so that I can ventilate a little or a lot, depending on whether I'm panting uphill or breezing downhill in the shade.