Can you spray herbicides such as a 3-way mixture in when the weather is still cold? And will it be effective? These weeds were sprayed at a temp average of about 40 degrees on March 28. And then at a temperature only slightly warmer of average for the day of 46 on April 7, 2013 . Weeds were yellow rocket. Both sprays appeared to work, or at least to result in major distortion and yellowing...so far.