SPF, or Sun Protection Factor, is a measure of how well a sunscreen protects our skin from UVB rays, the kind of radiation we know to cause sunburns and contribute to skin cancer. 😬 The number itself represents the factor of UVB protection the sunscreen provides: for instance, an SPF 30 sunscreen would allow 1/30th of UVB rays pass through. So if our skin would normally burn after 10 minutes in the sun, applying an SPF 30 sunscreen would theoretically allow us to stay in the sun without burning for approximately 300 minutes (a factor of 30 times longer). The estimate is rough because it also depends on skin type, intensity of sunlight, and amount of sunscreen used ☝ . Little note: Because of their inverse relationship, higher SPF values result in diminishing gains with respect to UVB attenuation. For instance, the difference between SPF 10 and 30 is muchhhh more than the difference between SPF 30 and 50, even though both numbers are off by the same difference in number. All said and done, I'd use a sunscreen with at least SPF 30 in these hot summer months ☀️😎☀️