Garden Blues

I just want to know if my garden will grow and when?  Everty spring in town we have a wk of warm weather followed by 3 wks of cold weather.  the plants stop growing and are asaulted by pests.. Last year it was in the 60,sF until june 26, then turned blazing hot.  on june 15 i journied to pasco..my corn was 5 ' high ..pasco 18 " high...This year, i,m using willow hoops and clear plastic...seems much better..it,s 80 today but will return to 60,s shortly..My plastic seems to give a 10 degree gain on cloudy days and soil temps r also higher..I,m hopeing for an extra month of growth degree days so my carrots and beets as well as tomatoes will grow. Last year my corn failed and my garden was iffy!  I put a lot of work in my garden...for naught... suggestions?