There are several potential reasons why you may have had poor fruit set in your vegetable garden.  

Unfavorable weather conditions are the primary reason for blossom drop and poor fruit set on tomatoes. High daytime temperatures (above 85 degrees Fahrenheit) and low nighttime temperatures (below 55 F) interfere with pollination, causing blossom drop. Optimal growing conditions for tomatoes are daytime temperatures of 70-85 F. (Cherry tomatoes set fruit over a wider temperature range than most large-fruited tomato cultivars.) Strong winds and dry soil conditions also may contribute to blossom drop. Strong winds desiccate flowers, while dry soil conditions stress tomato plants.  Excessive fertilization (in particular excessive nitrogen) can also lead to poor fruit set.  Plants grow lots of great looking foliage, but very little, if any, fruit set.
Favorable weather and good care should result in good fruit set. Deeply water tomato plants once a week during dry weather.

Squash and other vine crops are monoecious. Monoecious plants have separate male and female flowers on the same plant. Male and female flowers are similar in appearance. However, female flowers have small, immature fruits at their base. Pollen is transferred from the male to the female flowers by bees and other pollinators. When properly pollinated and fertilized, the female flowers develop into fruit. The first flowers to appear on squash and other vine crops are predominately male. As a result, fruit production is poor when the plants begin to flower. The squash plants should begin producing a good crop within a few weeks as the number of female flowers increases.
Unfavorable weather and the use of insecticides also can affect fruit set on vine crops. Cool, rainy weather during bloom reduces bee activity. Fewer bees visiting the garden results in poor pollination and poor fruit set. Apply insecticides in the garden only when necessary to avoid harming bees and other pollinators.

We are also at the very beginning of the fruiting season for tomatoes and some squash, especially winter squash.  There is still plenty of time for fruit to form.

A soil test would be a good idea to understand the soil fertility.  Both over and under fertility would lead to poor fruit set.
More information on soil testing can be found here: https://yardandgarden.extension.iastate.edu/soil-testing-resources-home-gardeners

Below are a few more resources that can help: 
https://yardandgarden.extension.iastate.edu/how-to/vegetable-planting-and-harvesting-times

https://yardandgarden.extension.iastate.edu/how-to/growing-tomatoes-home-garden

https://yardandgarden.extension.iastate.edu/how-to/managing-tomato-diseases-disorders-and-pests#failure

https://yardandgarden.extension.iastate.edu/how-to/growing-squash-iowa

https://yardandgarden.extension.iastate.edu/how-to/growing-squash-iowa#problems

Further questions can be directed to your local county Extension office. This local resource is very helpful since they are familiar with trends and issues in your part of the state. Click on this link to get connected directly with a staff person in your county Extension office and ask your gardening question. https://yardandgarden.extension.iastate.edu/ask-gardening-question

--Aaron