Tomato cracking results in some varieties of tomatoes more than others. It appears as either radial from the stem or circular around the stem. It is due to uneven movement of water in the plant. Maintaining even, adequate moisture through mulching is one of the best ways to prevent cracking. However, some varieties that have thinner skins may crack when there is a downpour due the rush of water movement from the roots into the plant. Certain cherry tomato and heirloom varieties are notorious for this with their thin skins. It can also occur with uneven watering. While we can't control when it rains a lot, we can alleviate tomato cracking with consistent and even watering and mulching. Some years are better than others. Here’s a link to tomato cracking from K-State Research and Extension.
https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Tomato%20Cracking.pdf
https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Tomato%20Cracking.pdf