I live in the back woods of Canada. We get a lot of snow. Our electrical supply (we call it "hydro") can disappear for long periods of time. The usual suspects are:
1. Ice storms. 3 inches (8 cm) of ice build up on trees can cause them to either drop limbs or deadfall into wires. It can be spectacular to see. Sparky.
2. The first heavy snowfall of the year can cause problems because although trees are trimmed every few years, they can grow pretty fast and either arch over the wires or are now tall enough to deadfall on the wires. By the time the later heavy snowfalls have come the danger trees have already dangered. The worst trees for this are the pines and spruces (and hemlocks and cedars but don't tend to grow as tall) since their boughs catch the snow and their new wood is actually pretty weak.
3. Drivers losing control. Doing 20 over the posted limit and passing a plow while the roads are greasy and visibility poor often results in taking out one or more poles while converting yourself into a casualty.
One large factor here is not that it takes a crew long to restore the lines, it's that the problems tend to occur in many sports over a large geographic region. There are only so many crews on shift and more remote places can be forced to wait for days while the townies get services right away. Our power was off one spring for three weeks a few years back after a derecho passed through a strip about 100 miles long by 20 miles wide. I'm still burning the wood for heat.
So, yeah, it's normal. Doesn't matter how good your make your infrastructure, nature is harsher.