After a little research I learned that you CAN put GFCI's in line but if you do, when one trips, they will probably all trip. The way around this is to branch off the hot wires before connecting to the first GFCI outlet so the next one is not powered off the load side of the outlet.

Which brings me back to figuring out how the wiring is laid out to all of these outlets.

You don't need to figure out where the cables are run.

At each box, wirenut the incoming hot to the outgoing hot and add a pigtail to the GFCI receptacle's "LINE" screw. Same with the neutral.

Don't attach anything to the "LOAD" screws on the GFCI.

That way, the GFCI is only protecting that outlet. Nothing downstream.

If you'd PREFER to just install a single GFCI at the most upstream outlet, this is how you can track down which is the most upstream.

(1) Identify all outlets on the circuit.

(2) Turn off power.

(3) Dismantle every outlet (and wirenutted connection in the box). Make sure that the loose wires aren't touching anything.

(4) Turn power on.

(5) Test each outlet to see which one has power coming into it. That's your first outlet in the circuit.

Instead of dismantling everything, it may be easier to 'guess' which one is the most upstream and dismantle that one. Turn the power back on and see if ALL of the other outlets are dead. If not, you guessed wrong and one of the other outlets with power is upstream. Repeat as necessary.

I should probably also add that individual GFCIs at the receptacles aren't protecting the wires in the wall.

It's possible that the GFCI breaker is tripping because of a ground fault in a wire between boxes. Maybe a nail went through a cable or something.

I don't know what the odds of that are versus just nuisance tripping (probably pretty small), but I thought I'd add that as food for thought.

Or maybe there's a ground fault in one of the receptacles. A wire that occasionally brushes up against something it shouldn't due to vibration or some other cause of movement.

How often is it tripping? Is it consistent? The leaf blower could have caused it, but if it's tripping in other situations then that may not be the problem.

Are all (or most of) your breakers GFCI? Maybe you should replace the breaker which serves the outside receptacle with a regular one, and replace the outside receptacle(s) with individual units, like Greg said above. With the current relatively low cost of GFCI receptacles, I would rather do it that way (individual GFCI receptacles).

GFIs do seem to get overly sensitive after some years. But if you changed the breaker and it still trips, you probably have a real ground fault somewhere. You should diagnose that problem before you do anything else.

OK that all makes sense. Easier to replace with GFCI outlets than I thought, now that you explain it.

If I understand correctly, if there is a wiring problem that is NOT in any of the outlets, and I change each outlet to a GFCI and the breaker to a regular one, the outlets will not trip as a result of the in-wall wiring issue. Only the breaker would, if enough total current was passing.

Nothing's really been done to the house except a new roof a couple years ago, but none of this wiring should have been encountered. I assume runs through the walls to all these outlets and does not even get near the ceiling since there are no lighting circuits on it.

I'm miles away but I will see if I can get my sister to make a note of when it trips and what's plugged in at the time.

Thanks for all the advice everyone.

"Only the breaker would, if enough total current was passing."

Well, sort of.

Just to dispel any possible confusion:

A GFI breaker implements two functions.

The first is overcurrent protection. The breaker trips if the total current drawn from the circuit exceeds the breaker's rating. For branch circuits this is normally 15 or 20 amps. The more it exceeds the breaker's rating, the faster the breaker trips.

The second is ground fault protection. The breaker trips if it detects that the current is asymmetrical across the power line. The amount of asymmetrical (ground fault) current that trips the GFI part of the breaker is MUCH lower than the current that trips the overcurrent part . (Confused yet?)

To explain this second function: it's not 100% accurate to describe it this way, but it's easier (I hope) to understand if you think of the electricity as going out the hot side of the receptacle and coming back in the neutral side. The GFI monitors both of these. If the amount of current coming back is less than the amount going out, some of it must be "leaking" to ground. That leakage might be going through a person or animal, risking shock or electrocution. So when the GFI sees that, it instantly opens, shutting off the power. With most GFIs, an imbalance (fault current) of 5 milliamps (0.005 amps) is enough to cause a trip.

I actually did not know that GFCI outlets had overcurrent protection just like a panel mounted circuit breaker. Seems redundant if there is already a circuit breaker.

I wonder if that leaf blower just draws too much current, or if something else was plugged in. I'll check into that.

No, sorry for the confusion, GFI receptacles do NOT normally provide overcurrent protection. I was talking about a GFI breaker, as I said near the beginning of the post.

Oh sorry, I read right through "GFI breaker" and was thinking 'receptacle'. Reading comprehension!