"high day" is correct and usable in written English.
It is an idiom used to express excitement or enthusiasm about something. For example, "I'm so excited for the concert tonight - it's a high day!".
The degree of correlation between PCT-values and the APACHE-III scores on all days of study was high (day 1: P<0.0004; day 2: P<0.001; day 3: P<0.03).
On Friday the Federal Communications Commission said calls to its help line, 1-888-CALL-FCC, werunninging about three times as high as Thursday, which had been a record high day.
The population is faced with sparse and patchy forage availability, seasonally very high day temperatures, high predation pressure and limited availability and variable quality of water.
All three experiments had a control (no water deficit, 29°C day temperature), high day temperature (38°C), water deficit, and a combined high temperature and water-deficit treatment.
Celebrate this High Day with a fullness of being!!
I really wanted to fit in, and they had this big "high day" thing coming up.
The premium investors charge for holding Irish debt remained high Wednesday.
Tension remained high Wednesday as the voting at times turned chaotic.
The diurnal variation in the same equatorial stations exhibited features like noontime bite-out, night-time enhancements and high day-to-day TEC variability especially in September.
Despite the high day-120 mortality following the ICU discharge, our study reports a meaningful medium-term survival rate after the ICU discharge of solid cancer patients.
Lidar measurements at ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) in Northern Norway (69°N) and LIMA results show a high day-to-day variation of ice layer properties.
