Life on Earth would be severely damaged, but humans may survive
Nitric acid with pH of 1.5 corresponds to 0.2% solution. From chemical perspective, this is very dilute. This concentration lacks oxidizing power that allows the acid to eat through many materials, like in a dramatized "Alien" movie. Still, 1.5 is very acidic. Infamous "acid rains" have pH only in 4+ range.
If 100 mm precipitation is a one-time event, things will go to normal. Many roofs will leak, and many cars corrode, but it all could be rebuild and replaced. The effect on crops would be more damaging, but most of those 100 mm will run away from from the fields. Water ecosystems will be damaged the most, because many organisms would not be able to survive after this rainfall. Some will go extinct, but eventually life will rebound. People caught in the open will suffer from skin burns, and, without medical treatment, may die. Chemically, nitric acid will react with many minerals and soil ingredients, eventually bringing pH to normal levels.
If 100mm acid rains will repeat indefinitely, life on Earth as we know it is doomed. Land and oceans can absorb some acid, but eventually all chemical sinks will be filled, and environment would turn to very acidic. Few organisms can survive at pH as low as 3. However, those few acidophiles will flourish and eventually replace all other life forms on Earth. Life will go on.
Humans, however, will be brought to a brink of extinction. All our food base will be destroyed. We can't turn ourselves into acidophiles, and can't readily use acidophiles as food source. In a short term, humans would need to find sturdy shelters and secure as much food and equipment as possible.
What would be a secure shelter? As I mentioned before, 0.2% is a diluted acid. Most existing roofs can't cope that, but that's mostly because of the use of iron nails and inadequate sealing. Acrylic plastic and glass can tolerate diluted acid with no problem.
Humans can secure and acidproof existing greenhouses. This would give us some food, though it would be sufficient only for a fraction of today's population.
Cars and locomotives would be unsalvageable. But we can make our machinery more resistant to this acid. Popular materials like stainless steel and brass are reasonably resistant to diluted acids, and protective coating can further improve resistance.
Humans can go out in this rain, if wearing full protective clothing, and cleaning those clothing with alkaline water afterwards.
Fossil fuels can still be burned, solar panels would still work (with sufficient sealing). Hydro and wind turbines would be more challenging because of high corrosion.
Overall, if humans can do it right, they will survive, as a race.