total #rows -- pressure now -- pressure 1/2 hour ago -- pressure 1 hour ago -- temperature -- humidity
125 -- 1017.2 -- 1017.3 -- 1017.5 -- -1.73 -- 100

prediction with 0.05 per half hour
falling pressure
Fairly Fine Showery Later

prediction with 0.5 per half hour
steady
Fine, Possibly showers

prediction with 2.5 per half hour
steady
Fine, Possibly showers

https://www.omnicalculator.com/physics/dew-point#how-to-calculate-dew-point-how-to-calculate-relative-humidity
Dewpoint Ts = (b * alpha(T,RH)) / (a - alpha(T,RH))
T is the temperature
RH is the relative humidity of the air
a and b are coefficients. For Sonntag90 constant set, a = 17.62 and b = 243.12 degC
alpha(T,RH) = ln(RH/100) + aT/(b+T)

ln(e) = 1 => 1.0000000631064
Dewpoint = -1.73

Crhusa
S1 = humidity
S2 = delta pressure / dewpoint