Every summer, as temperatures rise and Americans head outside, dermatologists repeat the same warning: watch your moles. But a new study published in Nature Communications is giving that advice a deeper scientific foundation. Researchers have discovered that the genes controlling how many moles you have also help determine your risk for the deadliest form of skin cancer. In other words, your mole count is not just a quirk of your appearance: It is a window into your biology, and, potentially, a powerful early warning sign.

What scientists found

Researchers analyzed the DNA of nearly 86,000 people of European ancestry and identified 29 regions of the genome that influence how many moles a person develops. That alone is a significant advance. But the more striking finding is what those genes are also doing: 28 of the same 29 genetic regions are also tied to melanoma risk.

What does this mean? It means the same biological machinery that determines how many moles you have appears to shape your susceptibility to the deadliest form of skin cancer.

The study, which builds on decades of twin and large-scale genomic research, also found that mole-count genetics overlap with immune system function and basic cell growth pathways. That suggests a high mole count reflects something deeper than just how your skin responds to the sun. It reflects how your body regulates cell growth overall.

The red hair paradox

One of the study's most striking findings involves the MC1R gene, commonly known as the red hair gene. Certain variants of this gene actually reduce the number of moles a person develops, but increase their melanoma risk. Researchers believe this is because the same variant disrupts the signaling process that forms moles in the first place, while also weakening the skin's defenses against UV damage. This results in fewer moles, but more vulnerable skin.

Why the weather connection matters

UV radiation from the sun is the primary environmental trigger for melanoma, and your UV exposure is directly tied to the weather and season. Summer sun is stronger, days are longer and people spend more time outdoors. That is exactly when UV levels peak.

The new study suggests that a high mole count captures cancer risk pathways that go beyond skin pigmentation. In other words, genetic risk runs deeper than just how easily you tan or burn. Understanding your genetic risk does not change the forecast, but it does change what that forecast means for you personally.

What this means for future prevention

Scientists used the newly identified genetic markers to build an improved risk score, which essentially acts as a genetic forecast for a person's likelihood of developing a large number of moles (or, as the researches call it, a "moliness" score).

While the score currently explains about 5% of the variation in mole counts between people, it represents a significant improvement over previous genetic tools, performing roughly twice as well. Researchers hope a score like this can eventually be integrated into standard melanoma screening, allowing doctors to identify high-risk patients earlier and provide them with extra medical monitoring.

The findings could also eventually point toward new drug targets, as the newly discovered biological pathways open up fresh avenues for skin cancer research.

For now, the seasonal guidance remains straightforward: when the UV index is high, cover up, wear sunscreen, and get your moles checked regularly, especially if you have a lot of them. And don't worry: The Weather Channel app's skin health page has you covered.