WARNING: TOMATOES ARE VERY SENSIBLE AT FAST-CHANGING TEMPERATURES. You may want to consider covering tomatoes later in time, right when they are starting to form on the plant. I live in Romania, and the past 4, 5 years or so were terrible for tomatoes because of the Climate change, just to get an idea, imagine temperatures of 25-35 celsius in one day, and the next day full on rain at around 15 celsius. That kind of change is terrible, especially when cold rain comes down on them after a full day of sitting in more than 25 celsius. The best you can do in your case, try using plastic to cover them during the night, and when the whether is changing fast. And make sure the wind doesn't take them off.