Tomatoes set fruit when the night time temperatures are between 55 and 75 degrees. If the temps at night get below 55, the plants will not set fruit. Some varieties will go a little lower, cherry tomatoes for example, may set fruit at 50 degrees.
Cold soil is bad, as tomatoes are tropical plants, and need warm conditions. Wet, heavy and cold soil is really poor for tomatoes. Tomatoes need a fast draining soil, because they do best with a lot of oxygen around the roots. This in not to say they don't like water. They need water, but soil that does not drain floats the air out, and starves the plant for air. Water heavily, and then don't water again until the soil is dry a couple of inches down. (1 inch for very small plants) Give the plants a big drink of water, then let that drain out and start to become dry on top to give the plants a big breath of air.
Tomatoes do not like highly acid soils. You may need to add some dolomite (limestone) in small amounts. Ph 6 to 7 is good. Many areas of Alaska will have very low ph values, and may reach as low as 4 to 5.
Stacking car tires, say 2 or 3 high, and filling with light and fluffy soil will warm up the roots when the sun shines on them. Covering the plants at night will conserve heat so that the fruit will set.
Any green tomato that falls below 45 degrees will NEVER ripen any more. This will halt the process. You can pick them at the first sign of color, (pink) but if they have ever gotten below 45 degrees, before or after picking, they will never ripen.
Poor mans wall-o-water...
Having built bridges for many years, I was always around road construction.When plastic culvert comes to the job, they were always packed and banded.Small pcs of 12" culvert packing make dandy tomato planters.You can even drill and fill the webs with water, and on those sunny days, they warm the roots.That black plastic heats like heck.I also scribe 2x material, and put bottoms in them and make flower planters.Hey...the price is right.GR
You can also help your plants produce bigger, better tomatoes by plucking the suckers when they appear on indeterminate types. The suckers are the shoots that appear between an established limb and the main stem of a tomato plant.
Here's a good read on it.
When it gets late in the year and growing season is short, I also like to prune off all new blossoms. That way the plant doesn't wast energy and nutrients on tomatoes that have no chance to mature. It goes into the ones already growing.
One last tip I got from my great aunt is when you are getting close to the first frost, pull the tomato plant up by the roots and hang them upside down in a cellar or your garage. The green tomatoes will keep for a long time and slowly ripen.
I thought we wern't supposed to use old tires any more. Don't they leech into the soil?