Watering is obviously very important in a heat wave, when plants demand more of it, but it’s just as important that you do it right. Water deeply to forestall evaporation and promote root growth. Keeping the full depth moist will stabilize soil temperature. Water when it’s cool in the morning to prepare plants for the hot day ahead. If the soil is dry, use a slow-then-fast method of first moistening the soil, letting it sit for a bit, and then soaking deeply. 

Your goal is to water the root zone, not the foliage, since water droplets on a hot day can scald plants. Consider options like drip irrigation, which loses less water to wind and evaporation. Such watering techniques also help you avoid garden pests, an important advantage during heat and drought conditions.

Take care not to over-water. Soil that’s too wet can damage roots and drown some plants. Use your finger to test the soil to determine if the soil is wet enough based on the individual plants in the area. Take care to keep the soil of seedlings, new transplants, and container plants consistently moist. For established plants, water every two to three days. And don’t let any soil get completely dry. Finally, if you know a heat wave is coming in a few days, start the new watering regime right away to best prepare your plants.

Source: housedigest.com