Plant dormancy is stress as well as seasonally induced. Clematis plants have the capability to perform and look beautiful for a long season.
Hydration is important as the summer draws on and you may think leaving your garden to the rainfall takes care of all of the water the plant needs. Regular, deep watering will help your clematis plants achieve the full season the plant is capable of achieving.
After the main bloom period, pruning or at least deadheading and trimming back the plant, along with fertilizer and water will help the plant pause, then resume growing and support healthy, attractive foliage as well as subsequent blooms.
In hottest weather avoid applying fertilizer to the plant, and consider mixing the fertilizer at a weaker ratio in the summer. Watering before you apply fertilizer of any sort is a good practice also.
Be vigilant throughout the season about slugs also. Many insects do not bother clematis, another great reason to plant more clematis and take care of them throughout the growing season, but slugs can damage clematis throughout the season if not controlled.