watering the vegetable garden when temperatures exceed 90 degrees
The following is a table developed in Texas for water requirements for vegetable crops.
The following publications notes different ways to apply the water and management practices to promote -- use of mulches, drip irrigation etc
New Jersey (Rutgers)
Hope that helps. The key is to not apply the water during the heat of the day if you are using overhead watering system -- but in the morning -- you will get more into the soil and less evaporation.
Hope that helps.
If not you may try contacting the Clark Co. Washington Extension Office.
1919 NE 78th Street
Vancouver, WA 98665
360-397-6060 Ext. 5738
Gardening Program Coordinator