For future reference this is what I meant by a self-contained reproducible example, it is an example of the solution described in the link I gave you, although I don't know how to fix the grid layout.
library(pheatmap)
library(purrr)
library(gridExtra)
THIera <- read.csv(sprintf("https://docs.google.com/uc?id=%s&export=download",
"1CtB_5jqmah5DUtu2S5FpTTaSFvkA7tUH"), row.names = 1)
THIgfd <- read.csv(sprintf("https://docs.google.com/uc?id=%s&export=download",
"1TF-h97HJqCjbLc-vYTf9_GR8H7OcFpXC"), row.names = 1)
THIhad <- read.csv(sprintf("https://docs.google.com/uc?id=%s&export=download",
"1c3Cmkg3jimUGucNnlhKAmKL-1p113xL3"), row.names = 1)
THImpi <- read.csv(sprintf("https://docs.google.com/uc?id=%s&export=download",
"1EziU-s_kDpOD2Yyhqj0M9HVJkWmD-64M"), row.names = 1)
THI_interim <- pheatmap(THIera, cluster_rows = FALSE, cluster_cols = FALSE, fontsize = 10, main = "Era-interim: Temperature-Humidity Index",
display_numbers = FALSE, cellwidth = 25, cellheight = 12, angle_col = "45", silent = TRUE)
THI_gfdl <- pheatmap(THIgfd, cluster_rows = FALSE, cluster_cols = FALSE,fontsize = 10, main = "GFDL-ESM2M: Temperature-Humidity Index",
display_numbers = FALSE, cellwidth = 25,cellheight = 12, angle_col = "45", silent = TRUE)
THI_hadgem <- pheatmap(THIhad, cluster_rows = FALSE, cluster_cols = FALSE,fontsize = 10, main = "HadGEM2-ES: Temperature-Humidity Index",
display_numbers = FALSE, cellwidth = 25,cellheight = 12, angle_col = "45", silent = TRUE)
THI_mpiesm <- pheatmap(THImpi, cluster_rows = FALSE, cluster_cols = FALSE,fontsize = 10, main = "MPI-ESM MR: Temperature-Humidity Index",
display_numbers = FALSE, cellwidth = 25,cellheight = 12, angle_col = "45", silent = TRUE)
plot_list <- ls(pattern = "THI_") %>%
map(~eval(as.name(.))[[4]])
grid.arrange(arrangeGrob(grobs = plot_list, ncol=2))

Created on 2019-08-24 by the reprex package (v0.3.0)