Allen and UrbanArchR, our temps here in MN are pretty different than yours but where we have what hubby calls sugar sand...very fine sand. For years we grew GIANT pumpkins on our property and the lesson we learned was that you need to water a little often. We water every other day for a short while...the water drains so fast in the sand that you don't need a lot but you should do it often. We've grown pumpkins that run 50-100lbs with just a little effort. We also use a lot of liquid fertilizer early on and then lightly throughout the season (as appropriate for the stage of growth). For tomatoes, I've always trimmed my tomatoes up so none of the branches touch the ground (or get water splashed up on the leaves). Also, plant the tomatoes DEEP. I pinch off up the branches up to half the height when planting and bury the plant as far as I can.