I don’t activate if the forecast calls for a high chance of rain. I’m happiest with a forecast for 0%. I’m OK up to about 20% chance. At about 30-40% chance, I’m comfortable doing a short single-hill activation in the morning, but I’ll avoid really long outings.
I got shut down early once, when fog turned to drizzle, and I ran down the side of a mountain in a thunderstorm twice. Other than that, my first 40+ summits were all dry. I’m just not set up to operate in the rain. You could try running a coax out from your tent to your antenna. Keep your radio dry, and don’t forget that if lightning happens, you’re a target, sitting on top of a mountain. (It sorta seems to cry out, “Strike me!” IMHO.)
I operate in the southeastern USA. I’ve activated in the summer. I’ve activated in the winter. I’ve activated when there was fresh snow on the ground. I’ve activated when there was a layer of ice on top of a snowfall. I’ve activated at 90+ degrees (Fahrenheit). I’ve activated at 15-20 degrees and 15-20 MPH wind.
Dress for the weather. Pack your equipment in waterproof containers if there’s any chance of rain. Bring plenty of water (and stash some extra water in your car, in case you finish your hike dry.)
Keep your log book dry, or use waterproof paper and waterproof ink.