One of the most popular pieces I’ve ever written for this site was Hiking in the Rain. I wrote that after hiking with a friend during an unexpected shower in late May that year. That was over 4 years ago and I’ve learned a lot.
Forecasts
In general, when a weather forecast indicates a 50% chance of precipitation it means that 50% of the forecast area will see at least 0.01 inch of rain (the smallest reported). That’s just a quick shower, so be informed but don’t let a 5 minute shower keep you indoors. You need to pay attention to the entire forecast before you make your plans.
Test your gear
Because gear fails. My rain gear failed on me during a weeks worth of rainy day hikes. The last day was the most miserable day I’ve ever spent hiking. I was soaked to the bone because of failed rain gear with temperatures dropping and rain changing to snow. I was borderline hypothermic, hungry (I didn’t dare eat fearing my temperature would drop even further) and exhausted (we had a rescue on that trip as well). That weekend, I went out and bought a new Paclite Jacket (aff) which I need to test out. If I’d tested my gear beforehand (I knew it was going to rain all week), I’d have bought that jacket before I started.
Be informed and double check. But if you wait for perfect conditions, you’ll never go.