The 2013 gardening season was bookended by a very hard freeze on May 1st (19 degrees F in Denver) and a week of rain starting September 9th that soaked gardens and caused record flooding along the Colorado Front Range and plains. The last spring freeze in Denver was May 5th (our average date) and first fall freeze October 4th (October 7th is average date).Gardeners who planted cool season crops in mid-March achieved a harvest before the May 1st hard freeze although bolting afterwards was an issue. Eighty degree temperatures arrived the last week of May (85 degrees F on May 26) that prompted decline of cool season crops.
For planting warm season crops forty degree lows continued through the end of May and consistent fifty degree F or above nights didn't arrive until June 9th. One 92 degree F day occurred June 3 and then a record 99 degrees F June 10th and 100 degrees F June 11th. Early planting of very warm season crops such as tomato or peppers was best delayed until June or done with water walls if planted earlier.
Vegetable gardeners who haven't considered temperature moderating devices such as water walls until now may want to rethink their approach. It is generally accepted that temperature swings will be more pronounced with worldwide climate change. Take advantage of mulches and season extending devices if you haven't already to achieve satisfactory harvests.