1) the heirloom and full-sized varieties (such as paste tomatoes, Brandywine, Beefsteak, Early Girl and the like) need 9+ hours of full, STRONG sunlight to provide a goodly amount of fruit. If you don’t have that much sunlight to work with (for instance, if you only have a porch, patio or deck and it is partly shaded), then a cherry tomato works really well for those situations. Up here with our long days but sun relatively low in the sky, we get that question all the time.
2) Also, if you’re in the northern tier of states (like Eldred), the Early Girl, Stupice, Glacier and other early-type varieties will do better because they don’t need as much growing season, and they don’t need as much heat during the growing season.
3) if you’re concerned that your little tomato will dry out during the heat of summer, you can bury most of the stalk/vine in the ground, leaving only the few youngest branches of leaves aboveground. The entire length of stem/vine will sprout roots, and all those extra roots will help pull in more moisture.
4) Also with irrigation, water deeply 1-2 times a week, at night, rather than watering every day. When you water deeply 1-2 times a week, during the cool of the evening, that sends a lot of water down deep into the ground. The roots “chase” that water, going deeper than they would otherwise. When you water just a little, every day, that actually encourages the roots to not go as deep, so the plant is more prone to drying out during extended hot weather. If you plant tomatoes early enough in the season, with as much stem/vine in the ground as possible, and water deeply right from the start, plus put some mulch on the soil surface, you can make those tomatoes almost drought-proof.