From a ladder, a hail bruise and a heat blister look like cousins. Round mark, granules gone, shingle clearly not right. Plenty of adjusters have written one as the other, and it costs the same either way. Call blistering hail and the file bounces at the desk with a note that stings. Call hail blistering and you have denied damage the policy owes for. The two do not look alike to a desk reviewer with the aerial imagery open and your photos side by side, so they cannot look alike to you on the roof.
What hail actually does to a shingle
Hail is an impact. Everything about the evidence follows from that one fact.
A hail strike crushes the granules into the asphalt and bruises the mat underneath. Press on it and it feels soft, like a bruise on an apple. On a fresh strike the granule loss looks scattered and forced, not clean. On a hard strike you will see the mat itself fractured, and that fracture is the money shot, because a blister cannot produce it.
Distribution tells the same story from farther away. Hail falls with the storm, so strikes cluster on the slopes that faced the wind and thin out on the sheltered sides. Within a slope the pattern is random. Nature does not space its hits evenly, and it does not put them only on the shingles that were already worn.
What a blister is
A blister is not an impact. It is a manufacturing and heat problem. Moisture or volatiles trapped in the asphalt expand, push a small dome up through the surface, and eventually the dome pops. What is left looks like a small crater with granules missing.
Look closer and the differences show. A popped blister exposes smooth asphalt, sometimes shiny, with edges that look raised or lipped. There is no bruise, no soft spot, no mat fracture. Blisters cluster in rashes that follow heat, not weather. You will find them on the slope over a poorly ventilated attic, in patches, on multiple shingles in a run, and they appear on slopes the storm never touched. Many roofs blister within a few years of installation and then sit stable for a decade.
Check the soft metals first
Before you argue with a shingle, look at the metal. Vents, turbine caps, pipe jack flashing, gutters, downspouts, window screens, the AC condenser fins. Hail big enough to bruise a shingle leaves dents in soft aluminum, and aluminum does not blister.
Shingle marks with clean soft metals is a question. Shingle marks with dented soft metals is an answer.
This is the first thing a desk reviewer checks and it should be the first thing you check. If every vent cap on the roof is clean and the gutters have no strikes, and you are about to call widespread hail damage, stop and look again at what you are calling hits.
The test square settles it
Chalk a 10 by 10 test square on each slope you are evaluating. Circle every mark inside it, then work the circles one at a time. For each mark, answer three questions. Does it have a bruise you can feel? Is the exposed material mat or smooth asphalt? Do the edges sit flat or raised?
Bruise, exposed mat, flat edges, that is a strike. No bruise, shiny asphalt, lipped edges, that is a blister. Mixed results are normal. Real roofs have both, and your count only includes the marks that pass the test. A test square with eight honest hits holds up better than one with twenty circles a reinspector can pick apart.
Photograph the square from standing height, then shoot two or three circled marks close up with something in frame for scale. The reviewer needs to see what you saw, at the same distance you saw it.
Write the note that answers the question
Whichever way you call it, your note should read like you knew the other answer was possible. If you are paying the slope, say why. “Random distribution on south and west slopes consistent with reported storm direction, mat fracture visible in photos 8 and 9, collateral strikes on ridge vent and gutters.” If you are calling it blistering, say why. “Marks show exposed asphalt with raised edges, no mat bruising, no collateral damage to soft metals, pattern present on all slopes including north.”
One note, three or four facts, photo references. The desk reviewer stops being a skeptic and becomes a witness.
When you are still not sure
Some roofs will not give you a clean answer, and pretending otherwise is how files come back. Check the date of loss against the storm data for the address. Look at the neighbors. A real hail event does not stop at the property line, so if the houses on both sides are clean, be careful. Walk the elevations again and let the collateral evidence carry the decision.
And if it is still a coin flip, get a second set of eyes before you submit, not after the file bounces. Asking early reads as diligence. Asking after a rejection reads as damage control.
Hail or blister is not a talent call. It is a checklist. Impact evidence, distribution logic, soft metal collateral, an honest test square, and a note that shows your work. Run it the same way on every roof and the call defends itself.