Here are the most common causes of tomato wilt: Lack of / Excess Water Tomato plants require approximately 1 inch of water per week. Plants may wilt badly when soils are dry, but will revive rapidly when they are watered. A thorough watering once a week during hot, dry weather should be sufficient. Apply water directly to the soil around the base of the plants with a garden or soaker hose. If an overhead sprinkler is used to water the tomatoes, water the plants in the morning to reduce foliar disease problems. Also, tomato plants wilt when they stand in water for very long time. If soils stay saturated plants will die.   Tomato diseases such as  Verticillium and Fusarium wilts are caused by soil-borne fungi that invade tomato plants through injured roots. The fungi spread into the water-conducting tissue (xylem) in the stem and block the flow of water to the foliage. Foliage of affected plants turns yellow, then wilts and dies. A cut through the lower stem of a dead plant often reveals a brownish discoloration of the vascular tissue. There is nothing that can be done for plants that have Verticillium or Fusarium wilts. Plants that die should be removed and destroyed. Crop rotation is of limited value as the vascular wilt fungi may survive in the soil for several years. The use of resistant varieties is the best way to prevent losses due to wilts. Resistant varieties may become infected but many plants survive and produce an acceptable crop. Resistant varieties are available in seed catalogs and at garden centers. The letters V and F following the variety name in seed catalogs or on seed packets denote varieties that are resistant to Verticillium and Fusarium wilts.  Wilt resistant tomato varieties that perform well include Jetstar, Better Boy, Burpee VF, and Celebrity. Tomato Spotted Wilt Virus: Tomato spotted wilt virus (TSWV) can cause stunting, wilting, bronzing of foliage, and brown or green rings on fruit. A virus disease, TSWV can infect plants in the greenhouse or in the field. Infected plants cannot be cured and should be removed from the garden. No tomato varieties are resistant to tomato spotted wilt virus.    Cultural practices for healthy tomatoes: 1. Improve garden soil by adding organic material such as compost. 2. Keep the plants growing vigorously with proper water and nutrients. 3. Plant tomatoes as far as possible from potatoes or walnut trees. 4. Space plants for maximum air circulation. 5. Purchase only certified, disease-free, disease-resistant plants or seeds 6. Plant in a well-drained, porous soil. Where possible, keep tomato fruit off the ground by staking or caging each plant or mulch the ground with black plastic, straw or hay. 7. When transplanting, discard and destroy all tomato seedlings with lesions on the stem and leaves. 8. Eliminate competition from weeds. 9. When the foliage is wet with fog, dew, or rain, do not cultivate or work with the plants. This spreads fungal spores from plant to plant. 10. In the home garden, harvest all ripe fruit at each picking. If left in the field, such fruit will decay, and serve as a source of infection for remaining fruit. 11. After harvest is completed, spade or plow under, compost, or burn all tomato vines. 12. Rotate 3 or 4 years before planting tomatoes in the same area. 13. Keep the garden clean of plant debris 14. Continually monitor for pests and other problems

Thanks for your help, that is what I thought, but I have never had several varieties in different parts of my garden develop this problem.

I think you are right about the hot wet weather contributing to the disease in your tomatoes. Warm humid weather creates an environment that promotes fungal spore development. Once it starts there is not a lot you can do. Next year, in addition to the above suggestions use a preventive fungicide spray before you see any evidence of disease. Check out the web site Gardening in Michigan. It has a lot of good information and may be helpful to you