I have been using a product called Wall O Water for the past 3 years.
They are water holding tubes that encompass your tomato plant. You are able to plant your young seedlings into the ground as early late April!
The benefits of the product allow the heat to be absorbed in the side walls, which will warm your soil, moderate the temperature inside and protect the plants from the evening cold temperatures.
I buy the original ones from the Producer “Wally” who lives in Dillon Montana.
A three pack costs approximately 12.00. They can be stored and reused for the following year.
I have been eating cherry tomatoes as early as mid June!