Sun exposure doesn't necessarily make the angiomas themselves worse, but it can make them more noticeable. When your surrounding skin tans, the contrast between the red angiomas and your skin tone becomes more pronounced. That said, sun protection is always important for overall skin health, regardless of whether you have cherry angiomas. Using good quality sunscreen can help prevent other skin issues and may reduce the visual prominence of the angiomas by preventing the surrounding skin from getting darker. If the increased visibility in summer is bothering you, that might be motivation to look into removal options.