Huh. This is interesting. I googled reasons why I didn't get many female flowers on my butternut squash, and found this:
This happens when the average daytime temperatures are above 90 degrees Fahrenheit and nighttime temperatures are above 70 degrees Fahrenheit.
The reason why high temperatures might be causing your squash to produce only male flowers is that under stressful conditions, the plant tends to conserve energy for the time when it can actually start pollinating.
When grown outdoors where temperature control isn’t possible, we suggest you start planting squash early in the spring. This way, you will get enough female flowers to bloom before temperatures rise in the hot summer months.
– Nitrogen Levels
Fertilizer is very important for your squash plants. It adds beneficial nutrients to the soil and leads to healthy, vigorous growth. However, excessive fertilizer use could be causing your female squash flowers production to be suppressed.
Worried about your female squash flowers not opening despite low temperatures? Watering could be the key here. Female squash flowers tend to grow more in number when the soil conditions are kept moist. On the other hand, keeping your soil mostly dry has been seen to encourage the growth of more male flowers.
Make sure you are giving your plant at least 2 inches of water twice a week during the summer.