Is it normal for condensate to drip from my furnace exhaust?

Some condensation at the exhaust vent is completley normal with a high efficiency furnace. That's literally where the name comes from. These units pull so much heat out of the exhaust that the water vapor in the flue gas turns into liquid water, and on a really cold morning you'll see vapor pluming out of the vent and dripping around the housing. Mine does the same thing when it's in the teens and the furnace is running long cycles. That said, a steady drip that keeps showing up near the exterior vent housing is worth a closer look. First thing I'd check is where the water is actually coming from. If it's condensation forming on the outside of the vent pipe and running down the wall, that's mostly cosmetic, though it can ice up the foundation in winter. If it's water coming out of the joint between the exhaust pipe sections or back out of the vent termination itself, the pipe slope might be off. On a 90% furnace the exhaust pipe should be pitched back toward the furnace so that water runs back to the internal condensate drain instead of pooling at the low point near the termination. If a hanger strap has come loose or the pipe shifted over time, water collects at the elbow and drips out at the seams. Also check wheather the exhaust termination is pointed too close to the wall. If it's angled back toward the house, the exhaust hits the siding and the moisture just runs down. Swinging the final elbow so it faces away from the wall usally cuts down on the wall staining and ice. Since your drain line outside looks clear, look at the condensate trap inside the furnace cabinet too. If that's partially plugged, water can back up and find odd paths. That's the one thing I'd want a tech to verify if everthing else checks out, since it's inside the cabinet and easy to misdiagnose yourself. But honestly, on cold mornings with the furnace running hard, seeing some water at the vent is just the unit doing what it's designed to do.

One thing I'd add from my own setup is that the drip itself can become the problem after a few hard freezes. Mine dripped for two winters, I ignored it, then one January morning the furnace short-cycled every ten minutes because the water had frozen into a lump right across the vent opening and the unit couldn't breathe properly. Once I chipped it off the cycling stopped. So even if the dripping is normal, I'd knock any ice buildup off the termination when it gets cold and keep an eye on whether the drips freeze faster than they evaporate. Also worth confirming which pipe is actually dripping if you have seperate intake and exhaust, since people mix them up all the time and end up watching the wrong one.

I agree that a steady drip near the vent housing is usually worth keeping an eye on, but some moisture is just part of how these units operate. My expirience has shown that the issue isn't always just ice buildup. On a diferent unit, the water accumulating inside the main vent elbow started forming a thick mineral scale over time. That scale eventually blocked the entire internal flow, which made the furnace run inefficiently even when it was operating in milder weather. It sounds like you've alredy looked at the slope of the pipe, so focusing on those internal blockages makes sense.

Is the water showing up on the intake pipe by any chance? People always blame the exhaust but the intake can be the culprit too. Cold outside air gets pulled through that pipe and warm humid basement air condenses right on the outside of it, same as a cold drink sweating. On my setup the intake runs through an unheated corner by the garage and I'd get a puddle at the base every cold snap. Wrapped four feet of it with foam pipe sleeve, maybe ten bucks, and the puddle was gone within a week. Feel both pipes after a long run and see which one is actually wet before you start moving elbows around.

You might be underestimating how much heat that exhaust pipe dumps into the surrounding structure. It isn't always just the moisture leaving the unit that causes the drip; sometimes the vent pipe itself acts like a massive heat conductor. If you've got older framing or poor insulation in the wall behind the termination, that intense heat transfers right into the cold siding or foundation, creating localized condensation on the exterior surface of the house. My old furnace used to be a monster, and I had a spot on the chimney chase that felt damp every winter even when the unit was off. You should look into wrapping the vent pipe in foam, even if it's already installed, to break that thermal bridge.

Update: turns out the last reply nailed it. The drip was coming from the intake pipe, not the exhaust. Cold air coming in was making the pipe sweat near the vent housing, worst on those cold mornings when the fan runs hard. Wrapped some pipe insulation around the exposed run inside and outside and the dripping stopped. Good call on checking the intake side.